Introduction

Macrolide antibiotics, which are protein-synthesis inhibitors, have effective antibacterial activity against bacterial strains, for example, Streptococcus pneumoniae, Streptococcus pyogenes, Haemophillus influenzae, Moraxella catarrhalis, Mycoplasma pneumoniae, Neisseria gonorrhoeae and so on, and have been used in clinical site over many years. Recently, resistant bacteria, especially S. pneumoniae with erm gene, have markedly increased,1, 2, 3 which cause serious problems in bacterial respiratory infections. Although clarithromycin4 and azithromycin5 are currently available in clinical site, they are partially influenced by efflux pumps produced by S. pneumoniae mef gene and are not effective enough against resistant bacteria such as S. pneumoniae and S. pyogenes with erm gene (Figure 1, Table 1). Telithromycin (TEL)6 is effective enough against S. pneumoniae with erm gene, but has potential to cause a serious liver damage7, 8 and loss of consciousness.9, 10 So, TEL has scarcely been used in Japan. Furthermore, the production cost of TEL is assumed to be relatively high owing to its complicated structure. Novel azalides11 were generated starting from 16-membered macrolides, and several optimized 16-membered azalides12 were effective against resistant S. pneumoniae and S. pyogenes with erm gene. These analogs are, however, still under research process and have not been developed yet. Currently available oral antibiotics are not effective enough against resistant bacteria with erm and mef genes, causing respiratory infections, and have some problems in safety or taste in clinical site.

Figure 1
figure 1

Chemical structures of clarithromycin, azithromycin, telithromycin, lincomycin and clindamycin.

Table 1 Antibacterial activities (MIC, μg ml−1) of the representative macrolides, LCM, CLDM and previously reported LCM derivatives (14)

Lincomycin (LCM)13, 14, 15, 16 was isolated as a secondary metabolite from the fermentation broth of Streptomyces lincolnensis. Clindamycin (CLDM)17 was synthesized by chemical modification of LCM and possessed a chlorine atom at the C-7 position with 7(S)-configuration. CLDM exhibited improved antibacterial activities compared with LCM, but it was also not effective against resistant pathogens with erm gene as in the case of LCM (Figure 1, Table 1).

LCM and CLDM inhibit protein synthesis of bacteria in a similar manner to macrolide antibiotics. X-ray crystallographic analysis18, 19, 20 indicated that CLDM had several major interactions by hydrogen bonding in 23S rRNA, and its binding site was closely located to that of macrolide antibiotics. Furthermore, they are effective against pathogens with mef gene in clinical isolate (Table 1). As an overview, CLDM exhibited the following positive characters: (1) availability of p.o. and i.v. administrations (switch therapy is possible), (2) good distribution to tissue and cells, (3) suppression21 of toxin production by Streptococcal strains and (4) expected reasonable production cost of CLDM derivatives. Thus, LCM derivatives might be more clinically valuable than macrolide antibiotics, if they are effective against pathogens with erm gene.

Chemical modifications at the C-7 position of LCM have been investigated by several research groups.16, 17, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34 One of their reports mentioned that 7(S)-7-O-methyllincomycin had stronger activities than 7(R)-7-O-methyllincomycin (7(S)-7-OMe>7(R)-7-OMe)27, 28 and it possessed 3.5 times stronger activities against Sarcina lutea than LCM. Derivatives possessing a larger alkoxy group or a substituted alkoxy group exhibited weaker antibacterial activities compared with LCM. On the other hand, 7(S)-7-alkylthio-7-deoxylincomycin and 7(S)-7-deoxy-7-(substituted-alkylthio)lincomycin were stronger than LCM against Gram-positive or Gram-negative organisms in vitro.29, 31 7(R)-7-Deoxy-7-(imidazol-2-yl-thio)lincomycin34 had similar antibacterial activities as LCM. According to the accumulated SAR information so far, a sulfur atom may be preferable to an oxygen atom to improve antibacterial activities in chemical modifications at the C-7 position of LCM. Furthermore, antibacterial activities are influenced by both configuration and structure of a substituent at the C-7 position.

X-ray crystallographic analyses18, 20 between bacterial ribosomal RNA and bacterial peptide-synthesis inhibitors, including CLDM and macrolide antibiotics, have already been reported. According to their reports, CLDM had enough three-dimensional empty space for an additional moiety around the C-7 position. So, we hypothesized that antibacterial activities may be improved by filling the above space with an appropriate substituent. We have reported synthesis and biological evaluation of several 7(S)-7-arylthio-7-deoxylincomycin derivatives so far.35, 36, 37, 38, 39, 40, 41 As far as we know, we reported LCM analogs possessing antibacterial activities against resistant pathogens with erm gene for the first time.35 We recently reported 7(S)-thiolincomycin analogs as the first-generation derivatives in our research. Compounds 1 and 2 (Figure 2) exhibited improved antibacterial activities against resistant S. pneumoniae with erm and mef genes compared with CAM, AZM, LCM and CLDM39 as shown in Table 1. Furthermore, we also reported novel derivatives 3 and 4,40 which had stronger activities than compounds 1 and 2. Comparing with compounds 14, we newly hypothesized that a benzene ring and a hetero ring with basicity are important to enhance antibacterial activities against resistant bacteria with erm and mef genes. In this article, we report synthesis and biological evaluation of novel LCM analogs possessing a benzene ring and a hetero ring with basicity via sulfur atom with the 7(S)-configuration.

Figure 2
figure 2

Previously reported LCM analogs modified at the C-7 position.

Results and Discussion

Synthesis of 7(S)-7-deoxy-7-(substituted-phenylthio)lincomycin derivatives

Synthesis of 7(S)-7-deoxy-7-(substituted-phenylthio)lincomycin derivatives is shown in Scheme 1. We have already reported synthetic route of compound 5.35, 36, 37, 40 We applied a different synthetic route for compound 5 from the previously reported route by Magerlein et al.25 We first prepared a key intermediate 5 derived from LCM in six steps in order to construct the same configuration at the C-7 position as CLDM in the final target molecules. A palladium-catalyzed cross-coupling reaction using 5 with various aryl halides is a widely applicable method to synthesize novel LCM derivatives in our research compared with Mitsunobu reaction or an SN2 reaction in application of a methanesulfonyl intermadiate.35, 36, 37, 40, 42 In this reaction, aryl halides such as aryl bromide, aryl iodide and aryl triflate can be used.42 Compounds 68, 1030, 3236 and 44 were synthesized by the cross-coupling reaction to investigate the antibacterial activities of aliphatic and aromatic amine compounds having a benzene ring and a basic moiety via sulfur atom at the C-7 position of LCM. Compound 9 was synthesized by reduction of a triple bond in compound 8 to evaluate its antibacterial activity compared with that of compound 6 or 7 focusing on the distance between a phenyl group and a dimethylamino group. Compound 31 was also prepared in application of Suzuki-Miyaura cross-coupling reaction from 30. This type of reaction, the palladium-catalyzed cross-coupling reaction of arylboronic acid with a LCM intermediate (30) possessing an aryl bromide moiety via sulfur at the C-7 position, was reported for the first time. The pyridine ring of compound 22 was reduced to give the corresponding piperidin-3-yl derivative (42). Then, compound 42 was converted to the desired N-methyl derivative (43) by reductive aminoalkylation. Compounds 42 and 43 were isolated as a mixture of each diastereoisomer.

Synthesis of 7(R)-7-deoxy-7-(4-(pyrimidin-5-yl)phenylthio)lincomycin

Synthesis of 7(R)-7-deoxy-7-(4-(pyrimidin-5-yl)phenylthio)lincomycin (41) is shown in Scheme 2. We prepared compound 41 possessing a 4-(pyrimidin-5-yl)phenyl group with 7(R)-configuration via sulfur atom at the C-7 position of LCM in order to evaluate its activity compared with that of compound 36 with the 7(S)-configuration. Preparation of 41 began with protection of all hydroxyl groups of CLDM. The protected compound 37 was reacted with potassium thioacetate by an SN2 reaction to give the corresponding thioacetate (38). Compound 39 was prepared by removing all TMS groups of compound 38 under the acidic condition and followed by the removal of the acetyl group to give a key intermediate 40. The desired pyrimidinylphenylthio derivative (41) with 7(R)-configuration was synthesized in application of 5-(4-bromophenyl)pyrimidine.

SAR analysis of LCM derivatives possessing an aliphatic amine as a substituent on the phenyl group at the C-7 position

Antibacterial activities of LCM derivatives possessing an aliphatic amine as a substituent on the phenyl group at the C-7 position via sulfur atom are shown in Table 2. As described above, we newly hypothesized that a benzene ring and a hetero ring with basicity were important to enhance antibacterial activities against resistant bacteria with erm gene. So, we first evaluated the distance between the phenyl group and the dimethylamino group in the C-7 substituent. As a result, compounds 6 and 7, which possessed one or two carbon atom(s) between the phenyl group and the dimethylamino group, exhibited relatively potent antibacterial activities against resistant S. pneumoniae with erm gene and H. influenzae compared with 9. Next, we fixed the number of carbon atom(s) between the phenyl group and the basic functionality as one or two, and we replaced the dimethylamino group with a hetero ring such as pyrrolidine, mono-N-methylpiperazine and piperidine. Consequently, compounds 10, 11 and 14 had similar antibacterial activities as compounds 6 and 7. On the other hand, we reported40 that a 2-(methoxymethyl)pyrrolidine group was an important moiety to enhance antibacterial activities against resistant bacteria with erm gene. Then, we introduced the 2-methoxymethyl group on the pyrrolidine ring of 10 to afford 15. Consequently, the desired product 15 exhibited four times potent activities against S. pneumoniae and S. pyogenes with erm gene compared with 10. These results suggest that a phenyl group and a basic moiety (especially, a hetero ring with a substituent) are important to enhance antibacterial activities against resistant bacteria with erm gene, and the number of carbon atoms between the phenyl group and the basic functionality might be optimized with one or two.

Table 2 Antibacterial activities (MIC, μg ml−1) of dimethylamino derivatives and cyclicaminoalkyl derivatives

SAR analysis of LCM derivatives possessing a heteroaryl group as a substituent on the phenyl group at the C-7 position

Novel aromatic derivatives possessing a phenyl or a heteroaryl group as a substituent on the phenyl group at the C-7 position via sulfur atom were synthesized and their antibacterial activities are shown in Table 3. Consequently, the heterocyclic substituent on the phenyl group at the C-7 position also improved antibacterial activities against resistant pathogens. Especially, compounds 19 and 22 had potent activities against resistant Streptococcus strains with erm gene and H. influenzae. Moreover, antibacterial activities of 22, when compared with those of 21 or 23 suggested that the location of the nitrogen atom was an important factor to enhance antibacterial activities.

Table 3 Antibacterial activities (MIC, μg ml−1) of a variety of heteroaromatic derivatives and compound 20

SAR analysis of LCM derivatives possessing a substituted phenyl or pyridinyl group as a substituent on the phenyl group at the C-7 position

Antibacterial activities of alternative biaryl derivatives possessing a substituted phenyl or pyridinyl group as a substituent on the phenyl group at the C-7 position are shown in Table 4. As a result, the 5-methoxypyridin-3-yl derivative (29) exhibited significantly stronger activities against resistant bacteria than the 3-methoxyphenyl derivative (25) or the 6-methoxypyridin-3-yl derivative (32). The pyridine analog (29) was shown to be the most potent among substituted pyridine analogs. However, it was less potent when compared with non-substituted pyridine analog (22).

Table 4 Antibacterial activities (MIC, μg ml−1) of substituted phenyl derivatives and substituted pyridinyl derivatives

SAR analysis of optimized LCM derivatives possessing a six-membered hetero ring as a substituent on the phenyl group at the C-7 position

Antibacterial activities of optimized LCM derivatives possessing a six-membered hetero ring as a substituent on the phenyl group at the C-7 position are shown in Table 5. A pyrimidine analog (36) exhibited slightly improved antibacterial activities compared with the pyridine-3-yl analog (22) against S. pneumoniae and H. influenzae. Moreover, non-aromatic derivatives 4244 also exhibited potent antibacterial activities against S. pneumoniae with erm gene and markedly improved activities against both S. pyogenes with erm gene and H. influenzae. We have already reported the importance of 7(S)-configuration to enhance antibacterial activities.39 Then, we also investigated the importance of 7(S) stereochemistry in pyrimidinylphenyl analogs. As a result, we could reconfirm that 7(S)-configuration was important to improve antibacterial activities based on the comparison results of potency between compound 36 (7(S)-configuration) and compound 41 (7(R)-configuration). According to the previously reported docking simulation analysis40 of 7(S)-7-deoxy-7-(4-morpholinocarbonylphenylthio)lincomycin, it was supposed that steric hindrance occurs between the 8-methyl group and a carbohydrate moiety in compound 41, and its three-dimensional structure is not appropriate for antibacterial activity.

Table 5 Antibacterial activities (MIC, μg ml−1) of optimized derivatives with a heterocycle and TEL

Conclusion

We were interested in LCM analogs possessing a phenyl ring and a hetero ring with basicity via sulfur atom focusing on the 7(S)-configuration at the C-7 position. We synthesized a variety of LCM analogs in application of the Pd-catalyzed cross-coupling reaction35, 36, 37, 40 of 7(S)-7-deoxy-7-thiolincomycin (5) with an aryl bromide or an aryl iodide. This methodology was very useful to synthesize various 7(S)-7-thio-modified LCM analogs. Antibacterial activities of LCM analogs with a linear moiety, which possessed one or two carbon atom(s) between the phenyl group and the dimethylamino group, were relatively effective against resistant bacteria. Furthermore, we found that the location of the nitrogen atom was important to improve antibacterial activities based on the results of compounds 2123. Consequently, we found that compounds 22, 36 and 4244 had potent antibacterial activities against S. pneumoniae and S. pyogenes with erm gene and H. influenzae. On the other hand, we confirmed that the 7(S)-configuration was important to enhance antibacterial activities in the comparison results of potency between compound 36 (7(S)-configuration) and compound 41 (7(R)-configuration). Antibacterial activities against S. pneumoniae with erm gene of our novel derivatives reported in this article were catching up with those of TEL, and the activities against S. pyogenes with erm gene and Streptococcus strains with mef gene of our selected derivative were stronger than those of TEL as shown in Table 5. We selected the 4-(pyrimidin-5-yl)phenyl group in compound 36 as the C-7 substituent for further medicinal chemistry toward generation of candidates, because it exhibits physicochemical stability without additional stereochemistry. In order to investigate other possibilities of novel semi-synthetic LCM antibiotics, alternative modifications of LCM analogs possessing a 7-thiothiadiazolyl group are in progress. On the basis of the information stated in this article, we will continually explore novel chemical modifications focusing on clinically promising LCM derivatives which exhibit potent antibacterial activities against resistant S. pneumoniae and S. pyogenes with erm and mef genes.

Experimental procedure

General methods

1H NMR spectra were measured with a BRUKER Ascend 400 NMR spectrometer (BRUKER, Coventry, UK) for 400 MHz, JEOL JNM-GSX 400 NMR spectrometer (JEOL,Tokyo, Japan) for 400 MHz or a Varian Gemini 300 NMR spectrometer (Varian, Palo Alto, CA, USA) for 300 MHz in CDCl3 or CD3OD. TMS (0 p.p.m.) in CDCl3 or CD3OD was used as an internal reference standard. Mass spectra (MS) were obtained on a JEOL JMS-700 mass spectrometer (JEOL) or Agilent Technologies 6530-Q-TOF LC/MS mass spectrometer (Agilent Technologies, Santa Clara, CA, USA). The optical rotations were recorded with Jasco P-2300 digital polarimeter (Jasco, Tokyo, Japan). Column chromatography was performed with silica gel (Wakogel C200, Wako Pure Chemical Industries, Osaka, Japan). Preparative thin-layer chromatography was performed with silica gel (Merck, Darmstadt, Germany: TLC plates Silica gel 60 F254). All organic extracts were dried over anhydrous MgSO4, and the solvent was removed with a rotary evaporator under reduced pressure.

7(S)-7-Deoxy-7-(4-((dimethylamino)methyl)phenylthio)lincomycin (6)

To a solution of 1-(4-bromophenyl)-N, N-dimethylmethanamine (23.2 mg, 0.108 mmol), 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene (Xantphos) (10.4 mg, 0.018 mmol) and tris(dibenzylideneacetone)dipalladium(0) (Pd2(dba)3) (8.3 mg, 9.6 μmol) in 1,4-dioxane (1 ml) were added to compound 5 (38.2 mg, 0.090 mmol) and N,N-diisopropylethylamine (31.4 μl, 0.180 mmol) and refluxed for 3 h. The mixture was filtrated by either Chromatodisc (0.45 μm) (KURABO INDUSTRIES, Osaka, Japan) or celite. The filtered solid were washed with MeOH three times and then the assembled solution was concentrated under reduced pressure. The resulting residue was purified by preparative TLC (CHCl3/MeOH/28% aq. NH4OH=10/1/0.1) to obtain the title compound as an off-white solid (39.4 mg, 78%). [α]D24 +98.0° (c 1.94, MeOH); ESI-MS m/z 556 (M+H)+ as C27H45N3O5S2; TOF-ESI-HRMS (M+H)+ calcd. for C27H45N3O5S2: 556.2879, found: 556.2883; 1H NMR (400 MHz, CD3OD) δ 0.89–0.98 (m, 3 H), 1.29 (d, J=6.9 Hz, 3 H), 1.31–1.41 (m, 4 H), 1.95–2.05 (m, 1 H), 1.97 (s, 3 H), 2.06–2.13 (m, 1 H), 2.13–2.22 (m, 1 H), 2.26 (s, 6 H), 2.41 (s, 3 H), 3.00 (dd, J=10.6, 4.6 Hz, 1 H), 3.25 (dd, J=8.1, 5.6 Hz, 1 H), 3.49 (s, 2 H), 3.58 (dd, J=10.2, 3.3 Hz, 1 H), 3.72–3.78 (m, 1 H), 3.87 (dq, J=6.9, 2.6 Hz, 1 H), 4.10 (dd, J=10.2, 5.6 Hz, 1 H), 4.34 (br dd, J=9.7, 0.5 Hz, 1 H), 4.42 (dd, J=9.7, 2.6 Hz, 1 H), 5.27 (d, J=5.6 Hz, 1 H), 7.26–7.32 (m, 2 H), 7.37–7.43 (m, 2 H).

7(S)-7-Deoxy-7-(4-(2-(dimethylamino)ethyl)phenylthio)lincomycin (7)

Compound 5 (106 mg, 0.251 mmol), 2-(4-bromophenyl)-N, N-dimethylethan-1-amine (124.9 mg, 0.547 mmol), Xantphos (15.8 mg, 0.027 mmol), Pd2(dba)3 (12.9 mg, 0.014 mmol) and N,N-diisopropylethylamine (64.0 μl, 0.368 mmol) in 1,4-dioxane (3 ml) were treated for 14 h according to the similar procedure as described for the preparation of 6 to afford 7 (85.7 mg, 60%) as a colorless solid. [α]D24 +102° (c 0.64, MeOH); ESI-MS (m/z) 570 (M+H)+ as C28H47N3O5S2; TOF-ESI-HRMS (M+H)+ calcd. for C28H47N3O5S2: 570.3035, found: 570.3034; 1H NMR (400 MHz, CD3OD) δ 0.88–0.98 (m, 3 H), 1.26 (d, J=6.8 Hz, 3 H), 1.30–1.42 (m, 4 H), 1.79–1.91 (m, 1 H), 1.95–2.04 (m, 1 H), 2.01 (s, 3 H), 2.05–2.12 (m, 1 H), 2.12–2.23 (m, 1 H), 2.31 (s, 6 H), 2.39 (s, 3 H), 2.52–2.60 (m, 2 H), 2.74–2.82 (m, 2 H), 2.98 (dd, J=10.7, 4.6 Hz, 1 H), 3.24 (dd, J=8.0, 5.6 Hz, 1 H), 3.58 (dd, J=10.2, 3.3 Hz, 1 H), 3.74 (m, 1 H), 3.81 (dq, J=6.8, 2.6 Hz, 1 H), 4.10 (dd, J=10.2, 5.5 Hz, 1 H), 4.33 (br dd, J=9.8, 0.5 Hz, 1 H), 4.39 (dd, J=9.8, 2.6 Hz, 1 H), 5.26 (d, J=5.5 Hz, 1 H), 7.17–7.24 (m, 2 H), 7.34–7.41 (m, 2 H).

7(S)-7-Deoxy-7-(4-(3-(dimethylamino)prop-1-yn-1-yl)phenylthio)lincomycin (8)

Compound 5 (66.2 mg, 0.157 mmol), 3-(4-bromophenyl)-N, N-dimethylprop-2-yn-1-amine (42.3 mg, 0.178 mmol), Xantphos (9.8 mg, 0.017 mmol), Pd2(dba)3 (6.5 mg, 7.1 μmol) and N,N-diisopropylethylamine (38.9 μl, 0.224 mmol) in 1,4-dioxane (0.75 ml) were treated for 14 h according to the similar procedure as described for the preparation of 6 to afford 8 (59.4 mg, 65%) as a colorless solid. FAB-MS (m/z) 580 (M+H)+ as C29H45N3O5S2; FAB-HRMS (M+H)+ calcd. for C29H45N3O5S2: 580.2879, found: 580.2878; 1H NMR (400 MHz, CD3OD) δ 0.85–1.00 (m, 3 H), 1.26–1.42 (m, 4 H), 1.34 (d, J=6.9 Hz, 3 H), 1.78–1.90 (m, 1 H), 1.92–2.03 (m, 1 H), 1.94 (s, 3 H), 2.03–2.11 (m, 1 H), 2.11–2.22 (m, 1 H), 2.37 (s, 6 H), 2.38 (s, 3 H), 2.97 (dd, J=10.6, 4.7 Hz, 1 H), 3.24 (dd, J=8.2, 5.7 Hz, 1 H), 3.48 (s, 2 H), 3.58 (dd, J=10.2, 3.2 Hz, 1 H), 3.75 (br dd, J=3.2, 0.6 Hz, 1 H), 3.89 (dq, J=6.9, 2.8 Hz, 1 H), 4.10 (dd, J=10.2, 5.6 Hz, 1 H), 4.36 (br dd, J=9.8, 0.6 Hz, 1 H), 4.45 (dd, J=9.8, 2.8 Hz, 1 H), 5.26 (d, J=5.6 Hz, 1 H), 7.35–7.42 (m, 4 H).

7(S)-7-Deoxy-7-(4-(3-(dimethylamino)propyl)phenylthio)lincomycin (9)

To a solution of compound 8 (21.4 mg, 0.037 mmol) in MeOH (2 ml) was added Pd/C (10.4 mg) and then vigorously stirred in hydrogen atmosphere at room temperature for 14 h. The mixture was filtrated with celite. The filtered solid was washed with MeOH three times and then the assembled solution was concentrated under reduced pressure. The resulting residue was purified by preparative TLC (CHCl3/CH3OH/28% aq. NH4OH=10/1/0.1) to obtain the title compound (9) (13.7 mg, 64%) as a colorless solid. [α]D23 +87.1° (c 0.22, MeOH); ESI-MS (m/z) 584 (M+H)+ as C29H49N3O5S2; TOF-ESI-HRMS (M+H)+ calcd. for C29H49N3O5S2: 584.3192, found: 584.3192; 1H NMR (400 MHz, CD3OD) δ 0.90–0.97 (m, 3 H), 1.26 (d, J=7.0 Hz, 3 H), 1.31–1.41 (m, 4 H), 1.76–1.91 (m, 3 H), 1.95–2.04 (m, 1 H), 2.01 (s, 3 H), 2.05–2.12 (m, 1 H), 2.12–2.23 (m, 1 H), 2.28 (s, 6 H), 2.39 (s, 3 H), 2.37–2.44 (m, 2 H), 2.62 (t, J=7.7 Hz, 2 H), 2.98 (dd, J=10.6, 4.6 Hz, 1 H), 3.24 (dd, J=8.1, 5.5 Hz, 1 H), 3.57 (dd, J=10.3, 3.3 Hz, 1 H), 3.73 (m, 1 H), 3.80 (dq, J=7.0, 2.4 Hz, 1 H), 4.10 (dd, J=10.3, 5.6 Hz, 1 H), 4.33 (br dd, J=9.8, 0.6 Hz, 1 H), 4.38 (dd, J=9.8, 2.4 Hz, 1 H), 5.26 (d, J=5.6 Hz, 1 H), 7.15–7.21 (m, 2 H), 7.34–7.39 (m, 2 H).

7(S)-7-Deoxy-7-(4-(pyrrolidin-1-ylmethyl)phenylthio)lincomycin (10)

Compound 5 (97.5 mg, 0.231 mmol), 1-(4-bromobenzyl)pyrrolidine (90.1 mg, 0.375 mmol), Xantphos (14.6 mg, 0.025 mmol), Pd2(dba)3 (11.1 mg, 0.012 mmol) and N,N-diisopropylethylamine (119.9 μl, 0.689 mmol) in 1,4-dioxane (2 ml) were treated for 3 h according to the similar procedure as described for the preparation of 6 to afford 10 (115.5 mg, 86%) as an off-white solid. [α]D23 +102° (c 3.96, MeOH); ESI-MS (m/z) 582 (M+H)+ as C29H47N3O5S2; TOF-ESI-HRMS (M+H)+ calcd. for C29H47N3O5S2: 582.3035, found: 582.3027; 1H NMR (400 MHz, CD3OD) δ 0.88–0.97 (m, 3 H), 1.28 (d, J=6.9 Hz, 3 H), 1.30–1.41 (m, 4 H), 1.75–1.83 (m, 4 H), 1.83–1.91 (m, 1 H), 1.98 (s, 3 H), 1.94–2.04 (m, 1 H), 2.05–2.11 (m, 1 H), 2.12–2.23 (m, 1 H), 2.40 (s, 3 H), 2.48–2.58 (m, 4 H), 2.99 (dd, J=10.6, 4.6 Hz, 1 H), 3.24 (dd, J=8.1, 5.6 Hz, 1 H), 3.59 (dd, J=10.2, 3.2 Hz, 1 H), 3.61 (s, 2 H), 3.72–3.76 (m, 1 H), 3.86 (dq, J=6.9, 2.6 Hz, 1 H), 4.11 (dd, J=10.2, 5.6 Hz, 1 H), 4.30–4.36 (m, 1 H), 4.42 (dd, J=9.7, 2.6 Hz, 1 H), 5.28 (d, J=5.6 Hz, 1 H), 7.28–7.34 (m, 2 H), 7.36–7.42 (m, 2 H).

7(S)-7-Deoxy-7-(4-(2-(pyrrolidin-1-yl)ethyl)phenylthio)lincomycin (11)

Compound 5 (83.0 mg, 0.196 mmol), 1-(4-bromophenethyl)pyrrolidine (50.0 mg, 0.197 mmol), Xantphos (11.0 mg, 0.019 mmol), Pd2(dba)3 (9.0 mg, 0.010 mmol) and N,N-diisopropylethylamine (172.5 μl, 0.990 mmol) in 1,4-dioxane (3 ml) were treated for 3 h according to the similar procedure as described for the preparation of 6 to afford 11 (82.0 mg, 70%) as a colorless solid. [α]D25 +68.0° (c 0.25, MeOH); ESI-MS (m/z) 596 (M+H)+ as C30H49N3O5S2; TOF-ESI-HRMS (M+H)+ calcd. for C30H49N3O5S2: 596.3192, found: 596.3171; 1H NMR (400 MHz, CD3OD) δ 0.89–0.97 (m, 3 H), 1.27 (d, J=6.9 Hz, 3 H), 1.31–1.42 (m, 4 H), 1.82–1.92 (m, 5 H), 1.95–2.04 (m, 1 H), 2.01 (s, 3 H), 2.05–2.12 (m, 1 H), 2.12–2.25 (m, 1 H), 2.39 (s, 3 H), 2.66–2.75 (m, 4 H), 2.75–2.89 (m, 4 H), 2.98 (dd, J=10.6, 4.6 Hz, 1 H), 3.24 (dd, J=8.0, 5.6 Hz, 1 H), 3.58 (dd, J=10.2, 3.3 Hz, 1 H), 3.71–3.76 (m, 1 H), 3.81 (dq, J=6.9, 2.5 Hz, 1 H), 4.10 (dd, J=10.2, 5.6 Hz, 1 H), 4.33 (br dd, J=9.8, 0.5 Hz, 1 H), 4.39 (dd, J=9.8, 2.5 Hz, 1 H), 5.26 (d, J=5.6 Hz, 1 H), 7.18–7.24 (m, 2 H), 7.34–7.41 (m, 2 H).

7(S)-7-Deoxy-7-(4-((4-methylpiperazin-1-yl)methyl)phenylthio)lincomycin (12)

Compound 5 (100.2 mg, 0.237 mmol), 1-(4-bromobenzyl)-4-methylpiperazine (144.3 mg, 0.536 mmol), Xantphos (14.6 mg, 0.025 mmol), Pd2(dba)3 (11.0 mg, 0.012 mmol) and N,N-diisopropylethylamine (119.9 μl, 0.689 mmol) in 1,4-dioxane (2 ml) were treated for 4 h according to the similar procedure as described for the preparation of 6 to afford 12 (132.7 mg, 92%) as a colorless solid. [α]D25 +93.2° (c 2.52, MeOH); ESI-MS (m/z) 611 (M+H)+ as C30H50N4O5S2; TOF-ESI-HRMS (M+H)+ calcd. for C30H50N4O5S2: 611.3301, found: 611.3285; 1H NMR (400 MHz, CD3OD) δ 0.88–0.97 (m, 3 H), 1.28 (d, J=6.8 Hz, 3 H), 1.28–1.41 (m, 4 H), 1.80–1.91 (m, 1 H), 1.95–2.04 (m, 1 H), 1.98 (s, 3 H), 2.04–2.12 (m, 1 H), 2.12–2.23 (m, 1 H), 2.27 (s, 3 H), 2.30–2.92 (m, 8 H), 2.40 (s, 3H), 2.99 (dd, J=10.7, 4.6 Hz, 1 H), 3.25 (dd, J=8.1, 5.7 Hz, 1 H), 3.51 (s, 2 H), 3.58 (dd, J=10.2, 3.3 Hz, 1 H), 3.71–3.77 (m, 1 H), 3.85 (dq, J=6.8, 2.6 Hz, 1 H), 4.10 (dd, J=10.2, 5.6 Hz, 1 H), 4.29–4.35 (m, 1 H), 4.41 (dd, J=9.8, 2.6 Hz, 1 H), 5.27 (d, J=5.6 Hz, 1 H), 7.26–7.33 (m, 2 H), 7.36–7.43 (m, 2 H).

7(S)-7-Deoxy-7-(4-(2-(4-methylpiperazin-1-yl)ethyl)phenylthio)lincomycin (13)

Compound 5 (90.0 mg, 0.213 mmol), 1-(4-bromophenethyl)-4-methylpiperazine (60.0 mg, 0.212 mmol), Xantphos (12.0 mg, 0.021 mmol), Pd2(dba)3 (9.7 mg, 0.011 mmol) and N,N-diisopropylethylamine (184.6 μl, 1.060 mmol) in 1,4-dioxane (3 ml) were treated for 2 h according to the similar procedure as described for the preparation of 6 to afford 13 (89.0 mg, 67%) as an off-white solid. [α]D23 +90.7° (c 2.05, MeOH); ESI-MS (m/z) 625 (M+H)+ as C31H52N4O5S2; TOF-ESI-HRMS (M+H)+ calcd. for C31H52N4O5S2: 625.3457, found: 625.3461; 1H NMR (400 MHz, CD3OD) δ 0.88–0.98 (m, 3 H), 1.26 (d, J=6.9 Hz, 3 H), 1.30–1.40 (m, 4 H), 1.79–1.92 (m, 1 H), 1.94–2.04 (m, 1 H), 2.00 (s, 3 H), 2.05–2.12 (m, 1 H), 2.12–2.23 (m, 1 H), 2.31 (s, 3 H), 2.39 (s, 3 H), 2.41–2.88 (m, 8 H), 2.58–2.64 (m, 2 H), 2.75–2.84 (m, 2 H), 2.99 (dd, J=10.6, 4.6 Hz, 1 H), 3.24 (dd, J=8.0, 5.6 Hz, 1 H), 3.58 (dd, J=10.2, 3.3 Hz, 1 H), 3.71–3.76 (m, 1 H), 3.80 (dq, J=6.9, 2.4 Hz, 1 H), 4.10 (dd, J=10.2, 5.6 Hz, 1 H), 4.31–4.35 (m, 1 H), 4.38 (dd, J=9.8, 2.4 Hz, 1 H), 5.26 (d, J=5.6 Hz, 1 H), 7.17–7.23 (m, 2 H), 7.34–7.40 (m, 2 H).

7(S)-7-Deoxy-7-(4-(piperidin-1-ylmethyl)phenylthio)lincomycin (14)

Compound 5 (98.1 mg, 0.232 mmol), 1-(4-bromobenzyl)piperidine (95.3 mg, 0.375 mmol), Xantphos (14.7 mg, 0.025 mmol), Pd2(dba)3 (10.8 mg, 0.012 mmol) and N,N-diisopropylethylamine (119.9 μl, 0.689 mmol) in 1,4-dioxane (2 ml) were treated for 3.5 h according to the similar procedure as described for the preparation of 6 to afford 14 (123.4 mg, 89%) as an off-white solid. [α]D23 +97.7° (c 4.26, MeOH); ESI-MS (m/z) 596 (M+H)+ as C30H49N3O5S2; TOF-ESI-HRMS (M+H)+ calcd. for C30H49N3O5S2: 596.3192, found: 596.3184; 1H NMR (400 MHz, CD3OD) δ 0.86–0.97 (m, 3 H), 1.29 (d, J=6.9 Hz, 3 H), 1.31–1.40 (m, 4 H), 1.40–1.50 (m, 2 H), 1.52–1.64 (m, 4 H), 1.79–1.91 (m, 1 H), 1.93–2.04 (m, 1 H), 1.98 (s, 3 H), 2.04–2.12 (m, 1 H), 2.12–2.23 (m, 1 H), 2.30–2.48 (m, 4 H), 2.39 (s, 3 H), 2.99 (dd, J=10.6, 4.6 Hz, 1 H), 3.24 (dd, J=8.1, 5.7 Hz, 1 H), 3.46 (s, 2 H), 3.59 (dd, J=10.2, 3.2 Hz, 1 H), 3.72–3.77 (m, 1 H), 3.86 (dq, J=6.9, 2.6 Hz, 1 H), 4.11 (dd, J=10.2, 5.6 Hz, 1 H), 4.30–4.36 (m, 1 H), 4.41 (dd, J=9.7, 2.6 Hz, 1 H), 5.28 (d, J=5.6 Hz, 1 H), 7.25–7.32 (m, 2 H), 7.35–7.41 (m, 2 H).

7(S)-7-Deoxy-7-(4-((2(S)-(methoxymethyl)pyrrolidin-1-yl)methyl)phenylthio)lincomycin (15)

Compound 5 (70.0 mg, 0.166 mmol), (S)-1-(4-bromobenzyl)-2-(methoxymethyl)pyrrolidine (96.5 mg, 0.340 mmol), Xantphos (9.7 mg, 0.017 mmol), Pd2(dba)3 (7.6 mg, 8.3 μmol) and N,N-diisopropylethylamine (87.6 μl, 0.503 mmol) in 1,4-dioxane (2 ml) were treated under microwave irradiation for 30 min according to the similar procedure as described for the preparation of 6 to afford 15 (61.0 mg, 59%) as a colorless solid. [α]D23 +72.0° (c 1.52, MeOH); ESI-MS (m/z) 626 (M+H)+ as C31H51N3O6S2; TOF-ESI-HRMS (M+H)+ calcd. for C31H51N3O6S2: 626.3298, found: 626.3297; 1H NMR (400 MHz, CD3OD) δ 0.88–0.98 (m, 3 H), 1.28 (d, J=6.9 Hz, 3 H), 1.31–1.40 (m, 4 H), 1.54–1.63 (m, 1 H), 1.64–1.75 (m, 2 H), 1.80–2.05 (m, 3 H), 2.00 (s, 3 H), 2.05–2.12 (m, 1 H), 2.12–2.22 (m, 1 H), 2.22–2.31 (m, 1 H), 2.40 (s, 3 H), 2.69–2.79 (m, 1 H), 2.84–2.91 (m, 1 H), 2.99 (dd, J=10.6, 4.6 Hz, 1 H), 3.24 (dd, J=8.1, 5.6 Hz, 1 H), 3.32–3.36 (m, 1 H), 3.33 (s, 3 H), 3.37–3.46 (m, 2 H), 3.58 (dd, J=10.2, 3.2 Hz, 1 H), 3.72–3.76 (m, 1 H), 3.85 (dq, J=6.9, 2.5 Hz, 1 H), 4.04–4.14 (m, 2 H), 4.31–4.37 (m, 1 H), 4.40 (dd, J=9.8, 2.5 Hz, 1 H), 5.27 (d, J=5.6 Hz, 1 H), 7.28–7.34 (m, 2 H), 7.36–7.41 (m, 2 H).

7(S)-7-Deoxy-7-(4-(thiazol-4-yl)phenylthio)lincomycin (16)

Compound 5 (100.0 mg, 0.237 mmol), 4-(4-bromophenyl)thiazole (100.0 mg, 0.416 mmol), Xantphos (10.0 mg, 0.017 mmol), Pd2(dba)3 (10.0 mg, 0.011 mmol) and N,N-diisopropylethylamine (82.6 μl, 0.474 mmol) in 1,4-dioxane (2 ml) were treated for 6 h according to the similar procedure as described for the preparation of 6 to afford 16 (93.6 mg, 68%) as a colorless solid. [α]D19 +98.1° (c 0.62, MeOH); ESI-MS (m/z) 582 (M+H)+ as C27H39N3O5S3; TOF-ESI-HRMS (M+H)+ calcd. for C27H39N3O5S3: 582.2130, found: 582.2131; 1H NMR (400 MHz, CD3OD) δ 0.89–0.96 (m, 3 H), 1.27–1.36 (m, 4 H), 1.36 (d, J=6.9 Hz, 3 H), 1.81–1.91 (m, 1 H), 1.95–2.04 (m, 1 H), 2.00 (s, 3 H), 2.05–2.13 (m, 1 H), 2.13–2.24 (m, 1 H), 2.40 (s, 3 H), 3.02 (dd, J=10.5, 4.8 Hz, 1 H), 3.23 (dd, J=8.2, 5.6 Hz, 1 H), 3.60 (dd, J=10.2, 3.3 Hz, 1 H), 3.74–3.79 (m, 1 H), 3.90 (dq, J=6.9, 2.6 Hz, 1 H), 4.11 (dd, J=10.2, 5.6 Hz, 1 H), 4.37–4.42 (m, 1 H), 4.45 (dd, J=9.7, 2.6 Hz, 1 H), 5.27 (d, J=5.6 Hz, 1 H), 7.48–7.54 (m, 2 H), 7.88–7.95 (m, 3 H), 9.05 (d, J=2.0 Hz, 1 H).

7(S)-7-Deoxy-7-(4-(1H-imidazol-1-yl)phenylthio)lincomycin (17)

Compound 5 (100.0 mg, 0.237mmol), 1-(4-bromophenyl)-1H-imidazole (70.0 mg, 0.314 mmol), Xantphos (10.0 mg, 0.017 mmol), Pd2(dba)3 (10 mg, 0.011 mmol) and N,N-diisopropylethylamine (82.6 μl, 0.474 mmol) in 1,4-dioxane (5 ml) were treated for 4 h according to the similar procedure as described for the preparation of 6 to afford 17 (56.5 mg, 42%) as a colorless solid. [α]D25 +97.8° (c 1.40, MeOH); ESI-MS (m/z) 565 (M+H)+ as C27H40N4O5S2; TOF-ESI-HRMS (M+H)+ calcd. for C27H40N4O5S2: 565.2518, found: 565.2522; 1H NMR (400 MHz, CD3OD) δ 0.89–0.96 (m, 3 H), 1.26–1.41 (m, 4 H), 1.34 (d, J=6.9 Hz, 3 H), 1.81–1.92 (m, 1 H), 1.96–2.06 (m, 1 H), 2.01 (s, 3 H), 2.06–2.14 (m, 1 H), 2.14–2.25 (m, 1 H), 2.43 (s, 3 H), 3.04 (dd, J=10.6, 4.8 Hz, 1 H), 3.25 (dd, J=8.3, 5.7 Hz, 1 H), 3.59 (dd, J=10.2, 3.2 Hz, 1 H), 3.78 (br dd, J=3.2, 0.5 Hz, 1 H), 3.91 (dq, J=6.9, 2.8 Hz, 1 H), 4.11 (dd, J=10.2, 5.5 Hz, 1 H), 4.37 (br dd, J=9.7, 0.5 Hz, 1 H), 4.48 (dd, J=9.7, 2.8 Hz, 1 H), 5.27 (d, J=5.5 Hz, 1 H), 7.14–7.17 (m, 1 H), 7.53–7.60 (m, 5 H), 8.13–8.17 (m, 1 H).

7(S)-7-Deoxy-7-(4-(1,3,4-thiadiazol-2-yl)phenylthio)lincomycin (18)

Compound 5 (100.0 mg, 0.237 mmol), 2-(4-bromophenyl)-1,3,4-thiadiazole (100.0 mg, 0.415 mmol), Xantphos (20.0 mg, 0.035 mmol), Pd2(dba)3 (20.0 mg, 0.022 mmol) and N,N-diisopropylethylamine (82.6 μl, 0.474 mmol) in 1,4-dioxane (2 ml) were treated for 6 h according to the similar procedure as described for the preparation of 6 to afford 18 (88.3 mg, 64%) as a colorless solid. [α]D20 +71.9° (c 0.40, MeOH); ESI-MS (m/z) 583 (M+H)+ as C26H38N4O5S3; TOF-ESI-HRMS (M+H)+ calcd. for C26H38N4O5S3: 583.2083, found: 583.2089; 1H NMR (400 MHz, CD3OD) δ 0.90–0.96 (m, 3 H), 1.28–1.41 (m, 4 H), 1.41 (d, J=6.9 Hz, 3 H), 1.82–1.94 (m, 1 H), 1.91 (s, 3 H), 1.98–2.08 (m, 1 H), 2.09–2.25 (m, 2 H), 2.45 (s, 3 H), 3.09 (dd, J=10.3, 4.7 Hz, 1 H), 3.29 (dd, J=7.9, 5.4 Hz, 1 H), 3.59 (dd, J=10.2, 3.2 Hz, 1 H), 3.79 (br dd, J=3.2, 0.5 Hz, 1 H), 4.03 (dq, J=6.8, 2.8 Hz, 1 H), 4.10 (dd, J=10.2, 5.6 Hz, 1 H), 4.39 (br dd, J=9.7, 0.5 Hz, 1 H), 4.54 (dd, J=9.7, 2.8 Hz, 1 H), 5.26 (d, J=5.6 Hz, 1 H), 7.52–7.57 (m, 2 H), 7.93–7.99 (m, 2 H), 9.43 (s, 1 H).

7(S)-7-Deoxy-7-(4-(1,2,3-thiadiazol-4-yl)phenylthio)lincomycin (19)

Compound 5 (100.0 mg, 0.237 mmol), 4-(4-bromophenyl)-1,2,3-thiadiazole (100.0 mg, 0.415 mmol), Xantphos (10.0 mg, 0.017 mmol), Pd2(dba)3 (10.0 mg, 0.011 mmol) and N,N-diisopropylethylamine (82.6 μl, 0.474 mmol) in 1,4-dioxane (3 ml) were treated for 6 h according to the similar procedure as described for the preparation of 6 to afford 19 (71.7 mg, 52%) as a colorless solid. [α]D20 +71.8° (c 0.35, MeOH); ESI-MS (m/z) 583 (M+H)+ as C26H38N4O5S3; TOF-ESI-HRMS (M+H)+ calcd. for C26H38N4O5S3: 583.2083, found: 583.2085; 1H NMR (400 MHz, CD3OD) δ 0.89–0.96 (m, 3 H), 1.26–1.38 (m, 4 H), 1.39 (d, J=6.9 Hz, 3 H), 1.82–1.93 (m, 1 H), 1.96–2.06 (m, 1 H), 1.98 (s, 3 H), 2.07–2.24 (m, 2 H), 2.44 (s, 3 H), 3.06 (dd, J=10.6, 4.8 Hz, 1 H), 3.26 (dd, J=8.3, 5.6 Hz, 1 H), 3.60 (dd, J=10.2, 3.2 Hz, 1 H), 3.78 (br dd, J=3.2, 0.6 Hz, 1 H), 3.96 (dq, J=6.9, 2.7 Hz, 1 H), 4.11 (dd, J=10.2, 5.6 Hz, 1 H), 4.41 (br dd, J=9.8, 0.6 Hz, 1 H), 4.49 (dd, J=9.8, 2.7 Hz, 1 H), 5.27 (d, J=5.6 Hz, 1 H), 7.55–7.60 (m, 2 H), 8.05–8.09 (m, 2 H), 9.25 (s, 1 H).

7(S)-7-([1,1′-Biphenyl]-4-ylthio)-7-deoxylincomycin (20)

Compound 5 (72.3 mg, 1.71 mmol), 4-bromo-1,1′-biphenyl (84.7 mg, 0.363 mmol), Xantphos (10.8 mg, 0.019 mmol), Pd2(dba)3 (8.1 mg, 8.8 μmol) and N,N-diisopropylethylamine (60.0 μl, 0.344 mmol) in 1,4-dioxane (1 ml) were treated for 4 h according to the similar procedure as described for the preparation of 6 to afford 20 (90.0 mg, 92%) as a colorless solid. [α]D26 +101° (c 1.16, MeOH); ESI-MS (m/z) 575 (M+H)+ as C30H42N2O5S2; TOF-ESI-HRMS (M+H)+ calcd. for C30H42N2O5S2: 575.2613, found: 575.2608; 1H NMR (400 MHz, CD3OD) δ 0.88–0.95 (m, 3 H), 1.25–1.40 (m, 4 H), 1.34 (d, J=6.9 Hz, 3 H), 1.79–1.90 (m, 1 H), 1.95–2.03 (m, 1 H), 2.02 (s, 3 H), 2.03–2.09 (m, 1 H), 2.10–2.21 (m, 1 H), 2.39 (s, 3 H), 2.99 (dd, J=10.6, 4.6 Hz, 1 H), 3.21 (dd, J=8.3, 5.8 Hz, 1 H), 3.60 (dd, J=10.2, 3.3 Hz, 1 H), 3.73–3.80 (m, 1 H), 3.88 (dq, J=6.9, 2.5 Hz, 1 H), 4.12 (dd, J=10.2, 5.5 Hz, 1 H), 4.36–4.41 (m, 1 H), 4.42 (dd, J=9.7, 2.5 Hz, 1 H), 5.28 (d, J=5.5 Hz, 1 H), 7.31–7.36 (m, 1 H), 7.39–7.46 (m, 2 H), 7.48–7.54 (m, 2 H), 7.56–7.64 (m, 4 H).

7(S)-7-Deoxy-7-(4-(pyridin-2-yl)phenylthio)lincomycin (21)

Compound 5 (70.6 mg, 0.167 mmol), 2-(4-bromophenyl)pyridine (77.8 mg, 0.332 mmol), Xantphos (11.4 mg, 0.020 mmol), Pd2(dba)3 (7.9 mg, 8.6 μmol) and N,N-diisopropylethylamine (58.0 μl, 0.333 mmol) in 1,4-dioxane (1 ml) were treated for 3 h according to the similar procedure as described for the preparation of 6 to afford 21 (87.9 mg, 91%) as a colorless solid. [α]D25 +86.7° (c 2.58, MeOH); ESI-MS (m/z) 576 (M+H)+ as C29H41N3O5S2; TOF-ESI-HRMS (M+H)+ calcd. for C29H41N3O5S2: 576.2566, found: 576.2558; 1H NMR (400 MHz, CD3OD) δ 0.88–0.95 (m, 3 H), 1.28–1.37 (m, 4 H), 1.37 (d, J=6.9 Hz, 3 H), 1.95–2.04 (m, 1 H), 1.95–2.05 (m, 1 H), 1.97 (s, 3 H), 2.05–2.11 (m, 1 H), 2.11–2.22 (m, 1 H), 2.41 (s, 3 H), 3.02 (dd, J=10.6, 4.8 Hz, 1 H), 3.23 (dd, J=8.3, 5.6 Hz, 1 H), 3.61 (dd, J=10.2, 3.2 Hz, 1 H), 3.76–3.82 (m, 1 H), 3.95 (dq, J=6.9, 2.6 Hz, 1 H), 4.13 (dd, J=10.2, 5.5 Hz, 1 H), 4.37–4.43 (m, 1 H), 4.49 (dd, J=9.7, 2.6 Hz, 1 H), 5.29 (d, J=5.5 Hz, 1 H), 7.34 (ddd, J=6.9, 5.0, 1.7 Hz, 1 H), 7.49–7.56 (m, 2 H), 7.81–7.91 (m, 2 H), 7.91–7.96 (m, 2 H), 8.61 (ddd, J=4.9, 1.6, 1.0 Hz, 1 H).

7(S)-7-Deoxy-7-(4-(pyridin-3-yl)phenylthio)lincomycin (22)

Compound 5 (109.3 mg, 0.259 mmol), 3-(4-bromophenyl)pyridine (89.7 mg, 0.383 mmol), Xantphos (15.2 mg, 0.026 mmol), Pd2(dba)3 (12.5 mg, 0.014 mmol) and N,N-diisopropylethylamine (88.9 μl, 0.511 mmol) in 1,4-dioxane (1.8 ml) were treated for 5.5 h according to the similar procedure as described for the preparation of 6 to afford 22 (131.0 mg, 88%) as a colorless solid. [α]D24 +83.9° (c 0.37, MeOH); ESI-MS (m/z) 576 (M+H)+ as C29H41N3O5S2; TOF-ESI-HRMS (M+H)+ calcd. for C29H41N3O5S2: 576.2566, found: 576.2573; 1H NMR (400 MHz, CD3OD) δ 0.89–0.96 (m, 3 H), 1.26–1.41 (m, 4 H), 1.36 (d, J=6.9 Hz, 3 H), 1.80–1.91 (m, 1 H), 1.96–2.05 (m, 1 H), 1.98 (s, 3 H), 2.05–2.12 (m, 1 H), 2.12–2.23 (m, 1 H), 2.41 (s, 3 H), 3.00 (dd, J=10.6, 4.6 Hz, 1 H), 3.24 (dd, J=8.1, 5.7 Hz, 1 H), 3.59 (dd, J=10.2, 3.3 Hz, 1 H), 3.76–3.80 (m, 1 H), 3.94 (dq, J=6.9, 2.7 Hz, 1 H), 4.11 (dd, J=10.2, 5.6 Hz, 1 H), 4.38 (br dd, J=9.7, 0.4 Hz, 1 H), 4.47 (dd, J=9.7, 2.7 Hz, 1 H), 5.27 (d, J=5.6 Hz, 1 H), 7.51 (ddd, J=8.0, 4.9, 0.7 Hz, 1 H), 7.54–7.58 (m, 2 H), 7.62–7.68 (m,2 H), 8.09 (ddd, J=8.0, 2.3, 1.6 Hz, 1 H), 8.52 (dd, J=4.9, 1.6 Hz, 1 H), 8.77–8.82 (m, 1 H).

7(S)-7-Deoxy-7-(4-(pyridin-4-yl)phenylthio)lincomycin (23)

Compound 5 (61.9 mg, 0.146 mmol), 4-(4-bromophenyl)pyridine (67.5 mg, 0.288 mmol), Xantphos (8.8 mg, 0.015 mmol), Pd2(dba)3 (6.9 mg, 7.5 μmol) and N,N-diisopropylethylamine (50.0 μl, 0.287 mmol) in 1,4-dioxane (1 ml) were treated for 6.5 h according to the similar procedure as described for the preparation of 6 to afford 23 (72.6 mg, 86%) as an off-white solid. [α]D25 +87.3° (c 2.15, MeOH); ESI-MS (m/z) 576 (M+H)+ as C29H41N3O5S2; TOF-ESI-HRMS (M+H)+ calcd. for C29H41N3O5S2: 576.2566, found: 576.2562; 1H NMR (400 MHz, CD3OD) δ 0.87–0.97 (m, 3 H), 1.26–1.40 (m, 4 H), 1.38 (d, J=6.9 Hz, 3 H), 1.80–1.92 (m, 1 H), 1.95 (s, 3 H), 1.97–2.07 (m, 1 H), 2.07–2.14 (m, 1 H), 2.14–2.24 (m, 1 H), 2.43 (s, 3 H), 3.04 (dd, J=10.6, 4.8 Hz, 1 H), 3.25 (dd, J=8.2, 5.6 Hz, 1 H), 3.61 (dd, J=10.2, 3.2 Hz, 1 H), 3.77–3.82 (m, 1 H), 3.97 (dq, J=6.9, 2.7 Hz, 1 H), 4.13 (dd, J=10.2, 5.6 Hz, 1 H), 4.35–4.43 (m, 1 H), 4.51 (dd, J=9.8, 2.7 Hz, 1 H), 5.28 (d, J=5.6 Hz, 1 H), 7.51–7.58 (m, 2 H), 7.68–7.78 (m, 4 H), 8.54–8.60 (m, 2 H).

7(S)-7-(3′-Cyano-[1,1′-biphenyl]-4-ylthio)-7-deoxylincomycin (24)

Compound 5 (85.2 mg, 0.202 mmol), 4'-bromo-[1,1'-biphenyl]-3-carbonitrile (104.0 mg, 0.403 mmol), Xantphos (12.7 mg, 0.022 mmol), Pd2(dba)3 (10.4 mg, 0.011 mmol) and N,N-diisopropylethylamine (69.9 μl, 0.402 mmol) in 1,4-dioxane (1 ml) were treated for 4 h according to the similar procedure as described for the preparation of 6 to afford 24 (49.4 mg, 41%) as a colorless solid. [α]D24 +91.6° (c 1.97, MeOH); ESI-MS (m/z) 600 (M+H)+ as C31H41N3O5S2; TOF-ESI-HRMS (M+H)+ calcd. for C31H41N3O5S2: 600.2566, found: 600.2559; 1H NMR (400 MHz, CD3OD) δ 0.88–0.97 (m, 3 H), 1.27–1.39 (m, 4 H), 1.35 (d, J=6.9 Hz, 3 H), 1.80–1.91 (m, 1 H), 1.95–2.05 (m, 1 H), 1.98 (s, 3 H), 2.06–2.21 (m, 1 H), 2.13–2.24 (m, 1 H), 2.42 (s, 3 H), 3.02 (dd, J=10.6, 4.6 Hz, 1 H), 3.24 (dd, J=8.1, 5.7 Hz, 1 H), 3.61 (dd, J=10.2, 3.3 Hz, 1 H), 3.76–3.81 (m, 1 H), 3.93 (dq, J=6.9, 2.7 Hz, 1 H), 4.12 (dd, J=10.2, 5.6 Hz, 1 H), 4.36–4.42 (m, 1 H), 4.48 (dd, J=9.7, 2.7 Hz, 1 H), 5.28 (d, J=5.6 Hz, 1 H), 7.50–7.55 (m, 2 H), 7.60–7.66 (m, 3 H), 7.67–7.71 (m, 1 H), 7.90–7.96 (m, 1 H), 7.96–8.00 (m, 1 H).

7(S)-7-Deoxy-7-(3′-methoxy-[1,1′-biphenyl]-4-ylthio)lincomycin (25)

Compound 5 (56.1 mg, 1.33 mmol), 4'-bromo-3-methoxy-1,1'-biphenyl (45.6 mg, 0.173 mmol), Xantphos (8.1 mg, 0.014 mmol), Pd2(dba)3 (6.3 mg, 6.9 μmol) and N,N-diisopropylethylamine (46.0 μl, 0.264 mmol) in 1,4-dioxane (1 ml) were treated for 6 h according to the similar procedure as described for the preparation of 6 to afford 25 (69.0 mg, 86%) as a colorless solid. [α]D24 +100° (c 2.76, MeOH); ESI-MS (m/z) 605 (M+H)+ as C31H44N2O6S2; TOF-ESI-HRMS (M+H)+ calcd. for C31H44N2O6S2: 605.2719, found: 605.2712; 1H NMR (400 MHz, CD3OD) δ 0.87–0.95 (m, 3 H), 1.24–1.37 (m, 4 H), 1.33 (d, J=6.9 Hz, 3 H), 1.79–1.89 (m, 1 H), 2.01 (s, 3 H), 1.95–2.09 (m, 2 H), 2.09–2.20 (m, 1 H), 2.38 (s, 3 H), 3.00 (dd, J=10.6, 4.8 Hz, 1 H), 3.20 (dd, J=8.3, 5.7 Hz, 1 H), 3.61 (dd, J=10.2, 3.3 Hz, 1 H), 3.74–3.79 (m, 1 H), 3.83 (s, 3 H), 3.88 (dq, J=6.9, 2.6 Hz, 1 H), 4.13 (dd, J=10.2, 5.5 Hz, 1 H), 4.36–4.42 (m, 1 H), 4.44 (dd, J=9.8, 2.6 Hz, 1 H), 5.29 (d, J=5.5 Hz, 1 H), 6.91 (ddd, J=8.2, 2.5, 0.9 Hz, 1 H), 7.11–7.14 (m, 1 H), 7.14–7.19 (m, 1 H), 7.30–7.37 (m, 1 H), 7.46–7.51 (m, 2 H), 7.54–7.59 (m, 2 H).

7(S)-7-(3′-Amino-[1,1′-biphenyl]-4-ylthio)-7-deoxylincomycin (26)

Compound 5 (66.9 mg, 0.158 mmol), 4′-bromo-[1,1'-biphenyl]-3-amine (75.9 mg, 0.306 mmol), Xantphos (10.0 mg, 0.017 mmol), Pd2(dba)3 (7.3 mg, 8.0 μmol) and N,N-diisopropylethylamine (53.5 μl, 0.307 mmol) in 1,4-dioxane (1 ml) were treated for 6 h according to the similar procedure as described for the preparation of 6 to afford 26 (47.6 mg, 51%) as a colorless solid. [α]D28 +142° (c 0.51, MeOH); ESI-MS (m/z) 590 (M+H)+ as C30H43N3O5S2; TOF-ESI-HRMS (M+H)+ calcd. for C30H43N3O5S2: 590.2722, found: 590.2713; 1H NMR (400 MHz, CD3OD) δ 0.89–0.95 (m, 3 H), 1.25–1.40 (m, 4 H), 1.33 (d, J=6.9 Hz, 3 H), 1.80–1.91 (m, 1 H), 1.95–2.05 (m, 1 H), 2.01 (s, 3 H), 2.05–2.21 (m, 2 H), 2.40 (s, 3 H), 3.02 (dd, J=10.5, 4.6 Hz, 1 H), 3.23 (dd, J=8.1, 5.6 Hz, 1 H), 3.60 (dd, J=10.2, 3.3 Hz, 1 H), 3.74–3.79 (m, 1 H), 3.86 (dq, J=6.9, 2.3 Hz, 1 H), 4.11 (dd, J=10.2, 5.6 Hz, 1 H), 4.36–4.41 (m, 1 H), 4.43 (dd, J=9.7, 2.3 Hz, 1 H), 5.27 (d, J=5.6 Hz, 1 H), 6.71 (ddd, J=7.9, 2.2, 0.9 Hz, 1 H), 6.92 (ddd, J=7.7, 1.7, 1.0 Hz, 1 H), 6.96–7.00 (m, 1 H), 7.13–7.19 (m, 1 H), 7.45–7.50 (m, 2 H), 7.52–7.57 (m, 2 H).

7(S)-7-Deoxy-7-(4-(5-fluoropyridin-3-yl)phenylthio)lincomycin (27)

Compound 5 (66.0 mg, 0.156 mmol), 3-(4-bromophenyl)-5-fluoropyridine (50.0 mg, 0.198 mmol), Xantphos (10.0 mg, 0.017 mmol), Pd2(dba)3 (10.0 mg, 0.011 mmol) and N,N-diisopropylethylamine (13.5 μl, 0.077 mmol) in 1,4-dioxane (1.5 ml) were treated for 3 h according to the similar procedure as described for the preparation of 6 to afford 27 (72.0 mg, 73%) as a colorless solid. [α]D25 +88.5° (c 1.78, MeOH); ESI-MS (m/z) 594 (M+H)+ as C29H40FN3O5S2; TOF-ESI-HRMS (M+H)+ calcd. for C29H40FN3O5S2: 594.2472, found: 594.2473; 1H NMR (400 MHz, CD3OD) δ 0.88–0.96 (m, 3 H), 1.26–1.40 (m, 4 H), 1.36 (d, J=7.0 Hz, 3 H), 1.79–1.92 (m, 1 H), 1.93–2.06 (m, 1 H), 1.97 (s, 3 H), 2.07–2.14 (m, 1 H), 2.14–2.24 (m, 1 H), 2.43 (s, 3 H), 3.04 (dd, J=10.5, 4.6 Hz, 1 H), 3.22–3.29 (m, 1 H), 3.60 (dd, J=10.1, 2.8 Hz, 1 H), 3.76–3.82 (m, 1 H), 3.93–4.01 (m, 1 H), 4.12 (dd, J=10.1, 5.5 Hz, 1 H), 4.36–4.41 (m, 1 H), 4.47–4.53 (m, 1 H), 5.28 (d, J=5.5 Hz, 1 H), 7.51–7.58 (m, 2 H), 7.64–7.71 (m, 2 H), 7.87–7.94 (m, 1 H), 8.41–8.47 (m, 1 H), 8.69 (s, 1 H).

7(S)-7-(4-(5-Cyanopyridin-3-yl)phenylthio)-7-deoxylincomycin (28)

Compound 5 (66.0 mg, 0.156 mmol), 5-(4-bromophenyl)nicotinonitrile (50.0 mg, 0.193 mmol), Xantphos (20.0 mg, 0.035 mmol), Pd2(dba)3 (10.0 mg, 0.011 mmol) and N,N-diisopropylethylamine (60.0 μl, 0.344 mmol) in 1,4-dioxane (1.5 ml) were treated for 6 h according to the similar procedure as described for the preparation of 6 to afford 28 (55.0 mg, 59%) as a colorless solid. [α]D25 +87.4° (c 0.81, MeOH); ESI-MS (m/z) 601 (M+H)+ as C30H40N4O5S2; TOF-ESI-HRMS (M+H)+ calcd. for C30H40N4O5S2: 601.2518, found: 601.2512; 1H NMR (400 MHz, CD3OD) δ 0.88–0.97 (m, 3 H), 1.29–1.41 (m, 4 H), 1.37 (d, J=6.8 Hz, 3 H), 1.83–1.92 (m, 1 H), 1.95 (s, 3 H), 1.98–2.08 (m, 1 H), 2.08–2.25 (m, 2 H), 2.44 (s, 3 H), 3.05 (dd, J=10.6, 4.8 Hz, 1 H), 3.27 (dd, J=8.1, 5.6 Hz, 1 H), 3.59 (dd, J=10.1, 3.2 Hz, 1 H), 3.79 (br dd, J=3.2, 0.6 Hz, 1 H), 3.98 (dq, J=6.8, 2.7 Hz, 1 H), 4.11 (dd, J=10.1, 5.6 Hz, 1 H), 4.39 (br dd, J=9.7, 0.6 Hz, 1 H), 4.50 (dd, J=9.7, 2.7 Hz, 1 H), 5.27 (d, J=5.6 Hz, 1 H), 7.53–7.60 (m, 2 H), 7.68–7.73 (m, 2 H), 8.45–8.49 (m, 1 H), 8.87 (d, J=1.8 Hz, 1 H), 9.08 (d, J=2.2 Hz, 1 H).

7(S)-7-Deoxy-7-(4-(5-methoxypyridin-3-yl)phenylthio)lincomycin (29)

Compound 5 (70.2 mg, 0.166 mmol), 3-(4-bromophenyl)-5-methoxypyridine (70.1 mg, 0.265 mmol), Xantphos (10.2 mg, 0.018 mmol), Pd2(dba)3 (8.1 mg, 8.8 μmol) and N,N-diisopropylethylamine (57.5 μl, 0.330 mmol) in 1,4-dioxane (1 ml) were treated for 6 h according to the similar procedure as described for the preparation of 6 to afford 29 (78.0 mg, 78%) as a colorless solid. [α]D26 +86.8° (c 2.82, MeOH); ESI-MS (m/z) 606 (M+H)+ as C30H43N3O6S2; TOF-ESI-HRMS (M+H)+ calcd. for C30H43N3O6S2: 606.2672, found: 606.2660; 1H NMR (400 MHz, CD3OD) δ 0.83–0.99 (m, 3 H), 1.27–1.39 (m, 4 H), 1.35 (d, J=7.0 Hz, 3 H), 1.80–1.91 (m, 1 H), 1.95–2.05 (m, 1 H), 1.99 (s, 3 H), 2.06–2.13 (m, 1 H), 2.13–2.24 (m, 1 H), 2.42 (s, 3 H), 3.03 (dd, J=10.6, 4.7 Hz, 1 H), 3.24 (dd, J=8.2, 5.6 Hz, 1 H), 3.61 (dd, J=10.1, 3.3 Hz, 1 H), 3.77–3.82 (m, 1 H), 3.90–3.98 (m, 1 H), 3.94 (s, 3 H), 4.13 (dd, J=10.1, 5.5 Hz, 1 H), 4.36–4.42 (m, 1 H), 4.49 (dd, J=9.8, 2.7 Hz, 1 H), 5.29 (d, J=5.5 Hz, 1 H), 7.50–7.56 (m, 2 H), 7.59 (br dd, J=2.7, 1.7 Hz, 1 H), 7.61–7.67 (m, 2 H), 8.21 (d, J=2.7 Hz, 1 H), 8.39 (d, J=1.7 Hz, 1 H).

7(S)-7-(4-Bromophenylthio)-7-deoxylincomycin (30)

Compound 5 (100.0 mg, 0.237 mmol), 1-bromo-4-iodobenzene (133.8 mg, 0.473 mmol), Xantphos (27.4 mg, 0.047 mmol), Pd2(dba)3 (21.7 mg, 0.024 mmol) and N,N-diisopropylethylamine (82.6 μl, 0.474 mmol) in 1,4-dioxane (1 ml) were treated for 3 h according to the similar procedure as described for the preparation of 6 to afford 30 (100.2 mg, 73%) as a colorless solid. 1H NMR (400 MHz, CD3OD) δ 0.87–0.98 (m, 3 H), 1.27–1.40 (m, 4 H), 1.31 (d, J=6.9 Hz, 3 H), 1.76–1.90 (m, 1 H), 1.93–2.03 (m, 1 H), 1.98 (s, 3 H), 2.06 (dd, J=10.1, 8.6 Hz, 1 H), 2.10–2.22 (m, 1 H), 2.37 (s, 3 H), 2.98 (dd, J=10.6, 4.6 Hz, 1 H), 3.22 (dd, J=8.1, 5.7 Hz, 1 H), 3.60 (dd, J=10.2, 3.2 Hz, 1 H), 3.72–3.79 (m, 1 H), 3.85 (dq, J=6.9, 2.7 Hz, 1 H), 4.12 (dd, J=10.2, 5.6 Hz, 1 H), 4.31–4.37 (m, 1 H), 4.42 (dd, J=9.7, 2.7 Hz, 1 H), 5.28 (d, J=5.6 Hz, 1 H), 7.31–7.37 (m, 2 H), 7.44–7.50 (m, 2 H).

7(S)-7-Deoxy-7-(4-(2-methoxypyridin-3-yl)phenylthio)lincomycin (31)

To a solution of compound 30 (100.2 mg, 0.173 mmol) in DMF (1 ml) and water (0.25 ml) were added Pd(PPh3)4 (12.5 mg, 0.011 mmol), 2-methoxypyridine-3-boronic acid (62.6 mg, 0.409 mmol) and Na2CO3 (37.6 mg, 0.355 mmol) and then stirred at 80 °C for 10 h. The solution were diluted with ethyl acetate and water, and then filtrated with celite. The filtered solid was washed with ethyl acetate three times. The obtained solution was extracted with ethyl acetate and then the organic layer was dried over Na2SO4, filtrated and concentrated under reduced pressure. The resulting residue was purified by preparative TLC (CHCl3/MeOH/28% aq NH4OH=10/1/0.1) to obtain the title compound as an off-white solid (74.1 mg, 71%). [α]D24 +97.8° (c 3.63, MeOH); ESI-MS (m/z) 606 (M+H)+ as C30H43N3O6S2; TOF-ESI-HRMS (M+H)+ calcd. for C30H43N3O6S2: 606.2672, found: 606.2670; 1H NMR (400 MHz, CD3OD) δ 0.87–0.96 (m, 3 H), 1.27–1.39 (m, 4 H), 1.35 (d, J=6.9 Hz, 3 H), 1.79–1.90 (m, 1 H), 1.96–2.04 (m, 1 H), 1.99 (s, 3 H), 2.06 (dd, J=10.2, 8.5 Hz, 1 H), 2.11–2.24 (m, 1 H), 2.39 (s, 3 H), 2.99 (dd, J=10.6, 4.6 Hz, 1 H), 3.23 (dd, J=8.3, 5.7 Hz, 1 H), 3.60 (dd, J=10.1, 3.2 Hz, 1 H), 3.74–3.79 (m, 1 H), 3.89 (dq, J=6.9, 2.5 Hz, 1 H), 3.93 (s, 3 H), 4.12 (dd, J=10.1, 5.6 Hz, 1 H), 4.35–4.40 (m, 1 H), 4.42 (dd, J=9.7, 2.5 Hz, 1 H), 5.27 (d, J=5.6 Hz, 1 H), 7.03 (dd, J=7.3, 5.0 Hz, 1 H), 7.44–7.55 (m, 4 H), 7.69 (dd, J=7.3, 1.8 Hz, 1 H), 8.11 (dd, J=5.0, 1.8 Hz, 1 H).

7(S)-7-Deoxy-7-(4-(6-methoxypyridin-3-yl)phenylthio)lincomycin (32)

Compound 5 (41.1 mg, 0.0973 mmol), 5-(4-bromophenyl)-2-methoxypyridine (38.6 mg, 0.146 mmol), Xantphos (11.3 mg, 0.0195 mmol), Pd2(dba)3 (8.9 mg, 0.0097 mmol) and N,N-diisopropylethylamine (33.9 μl, 0.195 mmol) in 1,4-dioxane (0.82 ml) treated for 6 h according to the similar procedure as described for the preparation of 6 to afford 32 (53.4 mg, 91%) as a colorless solid. [α]D29 +96.1° (c 2.60, MeOH); ESI-MS (m/z) 606 (M+H)+ as C30H43N3O6S2; TOF-ESI-HRMS (M+H)+ calcd. for C30H43N3O6S2: 606.2672, found: 606.2664; 1H NMR (400 MHz, CD3OD) δ 0.87–0.96 (m, 3 H), 1.27–1.37 (m, 4 H), 1.33 (d, J=6.8 Hz, 3 H), 1.79–1.91 (m, 1 H), 1.96–2.04 (m, 1 H), 2.01 (s, 3 H), 2.04–2.10 (m, 1 H), 2.11–2.22 (m, 1 H), 2.40 (s, 3 H), 3.01 (dd, J=10.6, 4.7 Hz, 1 H), 3.22 (dd, J=8.1, 5.7 Hz, 1 H), 3.61 (dd, J=10.2, 3.3 Hz, 1 H), 3.75–3.80 (m, 1 H), 3.89 (dq, J=6.8, 2.6 Hz, 1 H), 3.93 (s, 3 H), 4.13 (dd, J=10.2, 5.6 Hz, 1 H), 4.36–4.40 (m, 1 H), 4.45 (dd, J=9.8, 2.6 Hz, 1 H), 5.29 (d, J=5.6 Hz, 1 H), 6.86 (dd, J=8.6, 0.6 Hz, 1 H), 7.46–7.58 (m, 4 H), 7.92 (dd, J=8.6, 2.6 Hz, 1 H), 8.37 (br dd, J=2.6, 0.6 Hz, 1 H).

7(S)-7-(4-(6-Aminopyridin-3-yl)phenylthio)-7-deoxylincomycin (33)

Compound 5 (100.0 mg, 0.237 mmol), 5-(4-bromophenyl)pyridin-2-amine (100.0 mg, 0.401 mmol), Xantphos (10.0 mg, 0.017 mmol), Pd2(dba)3 (10.0 mg, 0.011 mmol) and N,N-diisopropylethylamine (10.0 μl, 0.057 mmol) in 1,4-dioxane (5 ml) were treated for 6 h according to the similar procedure as described for the preparation of 6 to afford 33 (18.0 mg, 13%) as a colorless solid. [α]D25 +101° (c 0.33, MeOH); ESI-MS (m/z) 591 (M+H)+ as C29H42N4O5S2; TOF-ESI-HRMS (M+H)+ calcd. for C29H42N4O5S2: 591.2675, found: 591.2678; 1H NMR (400 MHz, CD3OD) δ 0.89–0.96 (m, 3 H), 1.25–1.40 (m, 4 H), 1.33 (d, J=6.9 Hz, 3 H), 1.80–1.91 (m, 1 H), 1.95–2.05 (m, 1 H), 2.03 (s, 3 H), 2.05–2.12 (m, 1 H), 2.12–2.21 (m, 1 H), 2.40 (s, 3 H), 3.01 (dd, J=10.6, 4.6 Hz, 1 H), 3.23 (dd, J=8.1, 5.4 Hz, 1 H), 3.59 (dd, J=10.2, 3.3 Hz, 1 H), 3.73–3.78 (m, 1 H), 3.85 (dq, J=6.9, 2.4 Hz, 1 H), 4.11 (dd, J=10.2, 5.6 Hz, 1 H), 4.36–4.40 (m, 1 H), 4.43 (dd, J=9.8, 2.4 Hz, 1 H), 5.27 (d, J=5.6 Hz, 1 H), 6.66 (dd, J=8.7, 0.7 Hz, 1 H), 7.46–7.55 (m, 4 H), 7.75 (dd, J=8.7, 2.4 Hz, 1 H), 8.17 (br dd, J=2.4, 0.7 Hz, 1 H).

7(S)-7-Deoxy-7-(4-(pyrazin-2-yl)phenylthio)lincomycin (34)

Compound 5 (100.0 mg, 0.237 mmol), 2-(4-bromophenyl)pyrazine (70.0 mg, 0.298 mmol), Xantphos (10.0 mg, 0.017 mmol), Pd2(dba)3 (10.0 mg, 0.011 mmol) and N,N-diisopropylethylamine (82.6 μl, 0.474 mmol) in 1,4-dioxane (2 ml) were treated for 4 h according to the similar procedure as described for the preparation of 6 to afford 34 (65.0 mg, 48%) as a colorless solid. [α]D19 +85.2° (c 1.01, MeOH); ESI-MS (m/z) 577 (M+H)+ as C28H40N4O5S2; TOF-ESI-HRMS (M+H)+ calcd. for C28H40N4O5S2: 577.2518, found: 577.2515; 1H NMR (400 MHz, CD3OD) δ 0.88–0.96 (m, 3 H), 1.27–1.38 (m, 4 H), 1.39 (d, J=6.9 Hz, 3 H), 1.82–1.92 (m, 1 H), 1.95 (s, 3 H), 1.97–2.07 (m, 1 H), 2.07–2.14 (m, 1 H), 2.14–2.24 (m, 1 H), 2.43 (s, 3 H), 3.05 (dd, J=10.6, 4.8 Hz, 1 H), 3.26 (dd, J=8.1, 5.6 Hz, 1 H), 3.60 (dd, J=10.2, 3.3 Hz, 1 H), 3.76–3.81 (m, 1 H), 3.99 (dq, J=6.9, 2.7 Hz, 1 H), 4.12 (dd, J=10.2, 5.6 Hz, 1 H), 4.40 (br dd, J=9.8, 0.6 Hz, 1 H), 4.51 (dd, J=9.8, 2.7 Hz, 1 H), 5.27 (d, J=5.6 Hz, 1 H), 7.53–7.58 (m, 2 H), 8.04–8.08 (m, 2 H), 8.52 (d, J=2.5 Hz, 1 H), 8.66 (dd, J=2.5, 1.5 Hz, 1 H), 9.10 (d, J=1.5 Hz, 1 H).

7(S)-7-Deoxy-7-(4-(pyrimidin-2-yl)phenylthio)lincomycin (35)

Compound 5 (105.7 mg, 0.250 mmol), 2-(4-bromophenyl)pyrimidine (116.3 mg, 0.495 mmol), Xantphos (15.0 mg, 0.026 mmol), Pd2(dba)3 (11.6 mg, 0.013 mmol) and N,N-diisopropylethylamine (86.0 μl, 0.494 mmol) in 1,4-dioxane (1.5 ml) were treated for 6 h according to the similar procedure as described for the preparation of 6 to afford 35 (134.0 mg, 93%) as a colorless solid. [α]D26 +83.6° (c 4.97, MeOH); ESI-MS (m/z) 577 (M+H)+ as C28H40N4O5S2; TOF-ESI-HRMS (M+H)+ calcd. for C28H40N4O5S2: 577.2518, found: 577.2512; 1H NMR (400 MHz, CD3OD) δ 0.86–0.95 (m, 3 H), 1.22–1.37 (m, 4 H), 1.39 (d, J=6.8 Hz, 3 H), 1.79–1.90 (m, 1 H), 1.93–2.07 (m, 2 H), 1.94 (s, 3 H), 2.07–2.23 (m, 1 H), 2.39 (s, 3 H), 3.00 (dd, J=10.6, 4.7 Hz, 1 H), 3.20 (dd, J=8.3, 5.9 Hz, 1 H), 3.63 (dd, J=10.2, 3.4 Hz, 1 H), 3.75–3.82 (m, 1 H), 3.99 (dq, J=6.8, 2.6 Hz, 1 H), 4.14 (dd, J=10.2, 5.5 Hz, 1 H), 4.38–4.43 (m, 1 H), 4.51 (dd, J=9.8, 2.6 Hz, 1 H), 5.30 (d, J=5.5 Hz, 1 H), 7.33 (t, J=4.9 Hz, 1 H), 7.47–7.54 (m, 2 H), 8.31–8.39 (m, 2 H), 8.82 (d, J=4.9 Hz, 2 H).

7(S)-7-Deoxy-7-(4-(pyrimidin-5-yl)phenylthio)lincomycin (36)

Compound 5 (69.5 mg, 0.164 mmol), 5-(4-bromophenyl)pyrimidine (74.6 mg, 0.317 mmol), Xantphos (10.1 mg, 0.017 mmol), Pd2(dba)3 (7.8 mg, 8.5 μmol) and N,N-diisopropylethylamine (55.0 μl, 0.316 mmol) in 1,4-dioxane (1 ml) were treated for 6 h according to the similar procedure as described for the preparation of 6 to afford 36 (74.7 mg, 79%) as an off-white solid. [α]D28 +142° (c 0.51, MeOH); ESI-MS (m/z) 577 (M+H)+ as C28H40N4O5S2; TOF-ESI-HRMS (M+H)+ calcd. for C28H40N4O5S2: 577.2518, found: 577.2508; 1H NMR (400 MHz, CD3OD) δ 0.88–0.96 (m, 3 H), 1.27–1.42 (m, 4 H), 1.37 (d, J=6.9 Hz, 3 H), 1.81–1.91 (m, 1 H), 1.96 (s, 3 H), 1.97–2.06 (m, 1 H), 2.06–2.13 (m, 1 H), 2.12–2.24 (m, 1 H), 2.43 (s, 3 H), 3.02 (dd, J=10.6, 4.8 Hz, 1 H), 3.25 (dd, J=8.3, 5.7 Hz, 1 H), 3.60 (dd, J=10.1, 3.2 Hz, 1 H), 3.77–3.82 (m, 1 H), 3.98 (dq, J=6.9, 2.8 Hz, 1 H), 4.12 (dd, J=10.1, 5.6 Hz, 1 H), 4.35–4.42 (m, 1 H), 4.50 (dd, J=9.7, 2.8 Hz, 1 H), 5.28 (d, J=5.6 Hz, 1 H), 7.54–7.60 (m, 2 H), 7.68–7.73 (m, 2 H), 9.07 (s, 2 H), 9.13 (s, 1 H).

7(S)-7-Chloro-7-deoxy-2,3,4-tris-O-(trimethylsilyl)lincomycin (37)

To a solution of CLDM (1.0 g, 2.353 mmol) in pyridine (5 ml) were added trimethylchlorosilane (1.19 ml, 9.389 mmol), hexamethyldisilazane (1.97 ml, 9.42 mmol) and stirred at room temperature for 2 h, then the solution was added to the saturated aqueous NaHCO3. The desired compound was extracted with hexane and then the organic phase was dried over Na2SO4, filtrated and concentrated under reduced pressure to obtain the title compound (1.47 g, 97%) as a colorless solid. ESI-MS (m/z) 641 (M+H)+ as C27H57ClN2O5SSi3; 1H NMR (400 MHz, CDCl3) δ 0.13 (s, 9 H), 0.14 (s, 9 H), 0.18 (s, 9 H), 0.84–0.94 (m, 3 H), 1.22–1.35 (m, 4 H), 1.44 (d, J=6.8 Hz, 3 H), 1.78–1.91 (m, 1 H), 1.92–2.10 (m, 3 H), 2.16 (s, 3 H), 2.41 (s, 3 H), 3.00 (dd, J=10.8, 3.7 Hz, 1 H), 3.18 (dd, J=7.3, 5.4 Hz, 1 H), 3.62 (dd, J=9.5, 2.4 Hz, 1 H), 3.74 (d, J=2.4 Hz, 1 H), 4.02 (d, J=9.9 Hz, 1 H), 4.16 (dd, J=9.5, 5.6 Hz, 1 H), 4.46–4.54 (m, 1 H), 4.56–4.64 (m, 1 H), 5.26 (d, J=5.6 Hz, 1 H), 7.67 (d, J=10.5 Hz, 1 H).

7(R)-7-Acetylthio-7-deoxylincomycin (39)

To a solution of compound 37 (1.47 g, 2.29 mmol) in DMF (10 ml) was added potassium thioacetatate (1.31 g, 11.4 mmol) and stirred at 100 °C for 18 h to give 7(R)-7-acetylthio-7-deoxy-2,3,4-tris-O-(trimethylsilyl)lincomycin (38). Compound 38 was dissolved with 1 N HCl and MeOH, and it was stirred at room temperature for 10 min. After the reaction mixture was washed with diethyl ether, ethyl acetate and the saturated aqueous NaHCO3 were added to the aqueous layer. The desired compound was extracted with ethyl acetate and then the organic layer was dried over Na2SO4, filtrated and concentrated under reduced pressure. The resulting residue was purified by silica gel column chromatography (CHCl3/CH3OH=50/1→10/1) to obtain the title compound (187.2 mg, 18%) as a colorless solid. ESI-MS (m/z) 465 (M+H)+ as C20H36N2O6S2; 1H NMR (400 MHz, CD3OD) δ 0.85–0.99 (m, 3 H), 1.26–1.42 (m, 4 H), 1.32 (d, J=7.1 Hz, 3 H), 1.75–1.88 (m, 1 H), 1.92–2.25 (m, 3 H), 2.16 (s, 3 H), 2.29 (s, 3 H), 2.38 (s, 3 H), 2.94 (dd, J=10.5, 5.1 Hz, 1 H), 3.21 (dd, J=8.6, 6.1 Hz, 1 H), 3.51 (dd, J=10.3, 3.3 Hz, 1 H), 3.72–3.77 (m, 1 H), 4.04 (dq, J=7.1, 3.7 Hz, 1 H), 4.08–4.13 (m, 1 H), 4.14–4.19 (m, 1 H), 4.44 (dd, J=9.4, 3.7 Hz, 1 H), 5.27 (d, J=5.6 Hz, 1 H).

7(R)-7-Deoxy-7-mercaptolincomycin (40)

To a solution of compound 39 (187.2 mg, 0.403 mmol) in MeOH (2 ml) was added 4.1 M sodium methoxide in MeOH solution (0.295 ml, 1.209 mmol) and stirred at room temperature for 20 min. The mixture was diluted with saturated aqueous NH4Cl and concentrated under reduced pressure. The resulting residue was diluted with ethyl acetate and 10% aqueous NaHCO3. Then, the desired compound was extracted with ethyl acetate, dried over Na2SO4 and concentrated under reduced pressure. The resulting residue was purified by silica gel column chromatography (CHCl3/CH3OH=50/1→10/1) to obtain the title compound (35.6 mg, 20%) as a colorless solid. ESI-MS (m/z) 423 (M+H)+ as C18H34N2O5S2; TOF-ESI-HRMS (M+H)+ calcd. for C18H34N2O5S2: 423.1987, found: 423.1982; 1H NMR (400 MHz, CD3OD) δ 0.88–0.97 (m, 3 H), 1.25–1.40 (m, 4 H), 1.33 (d, J=7.0 Hz, 3 H), 1.77–1.88 (m, 1 H), 1.95–2.09 (m, 2 H), 2.11 (s, 3 H), 2.16–2.27 (m, 1 H), 2.41 (s, 3 H), 2.97 (dd, J=10.5, 4.8 Hz, 1 H), 3.21 (dd, J=8.4, 6.1 Hz, 1 H), 3.33–3.41 (m, 1 H), 3.55 (dd, J=10.2, 3.3 Hz, 1 H), 3.80–3.85 (m, 1 H), 4.09 (dd, J=10.2, 5.6 Hz, 1 H), 4.20–4.30 (m, 2 H), 5.24 (d, J=5.6 Hz, 1 H).

7(R)-7-Deoxy-7-(4-(pyrimidin-5-yl)phenylthio)lincomycin (41)

Compound 40 (35.6 mg, 0.084 mmol), 5-(4-bromophenyl)pyrimidine (23.8 mg, 0.101 mmol), Xantphos (9.7 mg, 0.017 mmol), Pd2(dba)3 (7.7 mg, 8.4 μmol) and N,N-diisopropylethylamine (29.4 μl, 0.169 mmol) in 1,4-dioxane (1 ml) were treated for 6.5 h according to the similar procedure as described for the preparation of 6 to afford 41 (21.8 mg, 45%) as a colorless solid. [α]D24 +142° (c 1.05, MeOH); ESI-MS (m/z) 577 (M+H)+ as C28H40N4O5S2; TOF-ESI-HRMS (M+H)+ calcd. for C28H40N4O5S2: 577.2518, found: 577.2510; 1H NMR (400 MHz, CD3OD) δ 0.88–0.96 (m, 3 H), 1.27–1.37 (m, 4 H), 1.38 (d, J=7.1 Hz, 3 H), 1.79–1.90 (m, 1 H), 1.95–2.05 (m, 1 H), 2.08 (dd, J=10.1, 8.7 Hz, 1 H), 2.14 (s, 3 H), 2.16–2.27 (m, 1 H), 2.46 (s, 3 H), 3.01 (dd, J=10.5, 5.0 Hz, 1 H), 3.24 (dd, J=8.4, 6.1 Hz, 1 H), 3.53 (dd, J=10.2, 3.3 Hz, 1 H), 3.74–3.78 (m, 1 H), 3.84 (dq, J=7.1, 3.8 Hz, 1 H), 4.08 (dd, J=10.2, 5.7 Hz, 1 H), 4.22 (d, J=9.4 Hz, 1 H), 4.45 (dd, J=9.4, 3.8 Hz, 1 H), 5.26 (d, J=5.7 Hz, 1 H), 7.54–7.61 (m, 2 H), 7.65–7.72 (m, 2 H), 9.06 (s, 2 H), 9.12 (s, 1 H).

7(S)-7-Deoxy-7-(4-(piperidin-3-yl)phenylthio)lincomycin (42)

To a solution of compound 22 (12.4 mg, 0.022 mmol) in MeOH (1 ml) were added 1 N HCl (0.1 ml) and Pt black (12.8 mg) and stirred at room temperature for 22 h under the hydrogen gas atmosphere. Then, Pt black (12.4 mg) was added to the solution and stirred at room temperature for 3 days under the hydrogen gas atmosphere. The mixture was filtrated with celite and concentrated under reduced pressure. The resulting residue was purified by preparative TLC (CHCl3/MeOH/28% aq. NH4OH=4/1/0.1) to obtain the title compound (4.2 mg, 34%) as a colorless solid. [α]D29 +97.9° (c 0.74, MeOH); ESI-MS (m/z) 582 (M+H)+ as C29H47N3O5S2; TOF-ESI-HRMS (M+H)+ calcd. for C29H47N3O5S2: 582.3035, found: 582.3028; 1H NMR (400 MHz, CD3OD) δ 0.88–0.99 (m, 3 H), 1.27 (d, J=6.9 Hz, 3 H), 1.30–1.41 (m, 4 H), 1.61–1.70 (m, 2 H), 1.77–1.90 (m, 2 H), 1.92–2.04 (m, 2 H), 1.98 (s, 3 H), 2.05–2.12 (m, 1 H), 2.12–2.23 (m, 1 H), 2.38 (s, 3 H), 2.59–2.78 (m, 3 H), 2.98 (dd, J=10.6, 4.7 Hz, 1 H), 3.40–3.12 (m, 2 H), 3.24 (dd, J=8.2, 5.6 Hz, 1 H), 3.58 (dd, J=10.2, 3.3 Hz, 1 H), 3.74 (br dd, J=3.3, 0.5 Hz, 1 H), 3.81 (dq, J=6.9, 2.6 Hz, 1 H), 4.10 (dd, J=10.2, 5.6 Hz, 1 H), 4.29–4.35 (m, 1 H), 4.38 (dd, J=9.8, 2.6 Hz, 1 H), 5.26 (d, J=5.6 Hz, 1 H), 7.18–7.24 (m, 2 H), 7.35–7.41 (m, 2 H).

7(S)-7-Deoxy-7-(4-(1-methylpiperidin-3-yl)phenylthio)lincomycin (43)

To a solution of compound 42 (17.9 mg, 0.031 mmol) in MeOH (1 ml) were added acetic acid (0.0175 ml, 0.306 mmol), 37% aqueous formaldehyde (0.0230 ml, 0.309 mmol) and sodium acetoxy borohydride (68.2 mg, 0.306 mmol) and stirred at room temperature for 40 min. The mixture was concentrated under reduced pressure. The resulting residue was purified by preparative TLC (CHCl3/MeOH/28% aq NH4OH=10/1/0.1) to obtain the title compound (13.9 mg, 76%) as a colorless solid. [α]D18 +91.0° (c 0.64, MeOH); ESI-MS (m/z) 596 (M+H)+ as C30H49N3O5S2; TOF-ESI-HRMS (M+H)+ calcd. for C30H49N3O5S2: 596.3192, found: 596.3177; 1H NMR (400 MHz, CD3OD) δ 0.89–0.97 (m, 3 H), 1.27 (d, J=6.9 Hz, 3 H), 1.31–1.39 (m, 4 H), 1.44–1.56 (m, 1 H), 1.69–1.82 (m, 1 H), 1.82–1.94 (m, 3 H), 1.95–2.05 (m, 1 H), 1.98 (s, 3 H), 2.06–2.13 (m, 1 H), 2.13–2.25 (m, 3 H), 2.39 (s, 6 H), 2.83 (tt, J=11.9, 3.4 Hz, 1 H), 2.95–3.06 (m, 3 H), 3.25 (dd, J=8.1, 5.7 Hz, 1 H), 3.57 (dd, J=10.2, 3.3 Hz, 1 H), 3.71–3.76 (m, 1 H), 3.82 (dq, J=6.9, 2.6 Hz, 1 H), 4.10 (dd, J=10.2, 5.6 Hz, 1 H), 4.30–4.35 (m, 1 H), 4.39 (dd, J=9.8, 2.6 Hz, 1 H), 5.25 (d, J=5.6 Hz, 1 H), 7.20–7.25 (m, 2 H), 7.35–7.42 (m, 2 H).

7(S)-7-Deoxy-7-(4-(1-methyl-1,2,5,6-tetrahydropyridin-3-yl)phenylthio)lincomycin (44)

Compound 5 (162.6 mg, 0.385 mmol), 5-(4-bromophenyl)-1-methyl-1,2,3,6-tetrahydropyridine (114.9 mg, 0.456 mmol), Xantphos (22.8 mg, 0.039 mmol), Pd2(dba)3 (17.7 mg, 0.019 mmol) and N,N-diisopropylethylamine (130.1 μl, 0.747 mmol) in 1,4-dioxane (2.5 ml) were treated for 6 h according to the similar procedure as described for the preparation of 6 to afford 44 (175.9 mg, 77%) as a colorless solid. [α]D17 +89.1° (c 1.63, MeOH); ESI-MS (m/z) 594 (M+H)+ as C30H47N3O5S2; TOF-ESI-HRMS (M+H)+ calcd. for C30H47N3O5S2: 594.3035, found: 594.3039; 1H NMR (400 MHz, CD3OD) δ 0.89–0.97 (m, 3 H), 1.30 (d, J=6.9 Hz, 3 H), 1.30–1.41 (m, 4 H), 1.80–1.91 (m, 1 H), 1.94–2.03 (m, 1 H), 1.98 (s, 3 H), 2.04–2.10 (m, 1 H), 2.11–2.22 (m, 1 H), 2.37 (s, 3 H), 2.41 (dt, J=6.1, 3.0 Hz, 2 H), 2.48 (s, 3 H), 2.62–2.69 (m, 2 H), 2.98 (dd, J=10.7, 4.7 Hz, 1 H), 3.22 (dd, J=8.1, 5.7 Hz, 1 H), 3.33–3.38 (m, 2 H), 3.58 (dd, J=10.2, 2.6 Hz, 1 H), 3.72–3.76 (m, 1 H), 3.84 (dq, J=6.9, 2.6 Hz, 1 H), 4.10 (dd, J=10.2, 5.6 Hz, 1 H), 4.32–4.37 (m, 1 H), 4.41 (dd, J=9.7, 2.6 Hz, 1 H), 5.26 (d, J=5.6 Hz, 1 H), 6.20–6.25 (m, 1 H), 7.33–7.37 (m, 2 H), 7.38–7.42 (m, 2 H).

In vitro antibacterial activity

Minimum inhibitory concentration (μg ml−l) was determined by the agar dilution method, which was described in Clinical and Laboratory Standards Institute (M7-A5 in 2000). Test strains of S. pneumoniae and S. pyogenes were subjected to seed culture using brain heart infusion agar (Becton Dickinson and Company, Tokyo, Japan) and 5% defibrinated horse blood. Test strains of H. influenzae were subjected to seed culture using sensitivity disk agar-N ‘Nissui’ (Nissui, Tokyo, Japan), 5% defibrinated horse blood, 5 μg ml−l Hemin and 15 μg ml−l nicotinamide adenine dinucleotide. A 5 μl portion of cell suspension of the test strains having about 106 CFU per ml was inoculated into sensitivity disk agar-N supplemented with 5% defibrinated horse blood, 5 μg ml−l Hemin and 15 μg ml−1 NAD, and incubated at 37 °C for 18–22 h. Then, the minimum inhibitory concentration was measured.

scheme 1

Synthesis of 7(S)-7-arylphenylthio-7-deoxylincomycin, 7(S)-7-deoxy-7-heteroarylphenylthiolincomycin or 7(S)-7-aminoalkylphenylthio-7-deoxylincomycin derivatives. Conditions were as follows: (a) Ar-Br, Xantphos, Pd2(DBA)3, iPr2NEt, dioxane, reflux, 2–21 h, (b) Pd/C, H2, MeOH, r.t., overnight, (c) (2-methoxypyridin-3-yl)boronic acid, Pd(PPh3)4, Na2CO3, DMF, H2O, 80 °C, 8 h, (d) Pt black, H2, MeOH, 1 N HCl, r.t., 11 days, (e) HCHO, AcOH, NaBH(OAc)3, MeOH, r.t., 30 min.

scheme 2

Synthesis of 7(R)-7-deoxy-7-thiolincomycin 40 and compound 41. Conditions were as follows: (a) TMSCl, HMDS, Py, r.t., 1 h, (b) KSAc, DMF, 100 °C, 18 h, (c) 1 N HCl, MeOH, r.t., 10 min, (d), NaOMe, MeOH, r.t., 20 min, (e) Xantphos, Pd2(DBA)3, iPr2NEt, dioxane, reflux, 6 h.