Total synthesis of cyrneines A–B and glaucopine C


The cyrneine diterpenoids represent a structurally intriguing subfamily of cyathane diterpenoids and could significantly induce neurite outgrowth. Therefore, the efficient synthesis of these natural products is of great importance. Herein, we present a route for the collective synthesis of cyrneines A, B, and glaucopine C. As the key precursor, the 5-6-6-tricyclic scaffold is efficiently constructed by employing a mild Suzuki coupling of heavily substituted nonactivated cyclopentenyl triflate and a chelation-controlled regiospecific Friedel-Crafts cyclization as key transformations. The stereoselective installation of the all-carbon quaternary center at C6 ring junction of the tricycle is achieved via Birch reductive methylation. Subsequently, a carbenoid-mediated ring expansion furnishes the essential 5-6-7-tricyclic core. Finally, manipulation of this core by several appropriately orchestrated conversions accomplishes a more step-economic synthesis of cyrneine A (20 steps), and the first synthesis of cyrneine B (24 steps) and glaucopine C (23 steps).


The cyathane diterpenoids compose a large family of natural products with greater than 100 members1,2,3. These molecules feature a common 5-6-7 fused tricarbocyclic core with most of which possessing two all-carbon quaternary stereocenters at the ring junctions with anti-orientation. The unique structural framework coupled with the diverse oxidation and unsaturation states around the ring periphery gives rise to the structural complexity and diversity. Biological evaluation revealed that cyathane diterpenoids exhibit a rich variety of biological activities such as antibiotics, antimicrobial, antitumor, anti-inflammatory, and most significantly, nerve growth factor (NGF)-regulating properties. Over the roughly 20 years, considerable total synthesis efforts have been conducted, and a number of molecules within the subclasses of allocyathin, erinacine, sarcodonin, cyathin, scabronine, and cyanthiwigin have been synthesized in enantioselective or racemic forms. Of note are important contributions from the groups of Nakada2, Ward4,5, Trost6,7, Danishefsky8, Stoltz9, Phillip10, Reddy11, Snider12,13, and others14,15.

The cyrneines A−E and glaucopine C16,17,18,19, isolated form the Sarcodon Cyrneus, are a novel subfamily of cyathane diterpenoids (Fig. 1a). Unique to the structures of this subfamily as compared with other subclasses2,3,4,5,6,7,8,9,10,11,12,13,14,15 is the extra oxidation at C1 (e.g., 1, 3, 5, and 6), or at both C1 and C4 (e.g., 2 and 4) in the five-membered ring. This causes considerable synthetic challenges resulting from the higher oxidation states as well as the increased stereocenters at C1 or C4, especially for compounds 2 and 4 bearing an allylic functionality at C4 and two vicinal quaternary centers at C4 and C9 ring junction. To date, only cyrneine A (1) has been synthesized by Gademann and co-workers20 with an elegant sequence of 24 steps from (-)-(R)-carvone (Fig. 1b). The key transformations involved a reductive Knoevenagel condensation, a Heck cyclization, and a Yamamoto ring expansion. On the other hand, biological evaluations showed the activity of this subfamily was markedly influenced by the minor structural differences. Among the molecules evaluated, cyrneines A (1) and B (2) could induce significantly the neurite outgrowth in PC12 cells and the expression of NGF in 1321N1 cells in a concentration-dependent manner. Thus, driven by the structural complexity, biological potential, and the interest for an in-depth SAR elucidation, it is of great importance to develop a strategically new route that could be used for efficient and versatile synthesis of these natural products and potential analogues. Herein, we report such a route as demonstrated by a more step-economic synthesis of cyrneine A (1), and the first synthesis of cyrneine B (2) and glaucopine C (3).

Fig. 1

Cyathane diterpenoid natural products. a The structures of cyrneines A−E and glaucopine C. The [5.6.7]-tricycle highlighted in blue circle indicates a common core structural motif shared by the natural products. b The key reactions included in Gademann’s synthesis of cyrneine A. Me methyl, Tf trifluoromethanesulfonyl, TBS tertiary-butyldimethylsilyl, dr diastereomeric ratio


Retrosynthetic analysis

We envisioned that the 5-6-7 tricyclic core A could serve as an advanced intermediate for our divergent synthesis (Fig. 2). The key challenge for accessing cyrneine A (1) and the intermediate B would be the β-selective reduction of carbonyl at C14 in A. The glaucopine C (3) and cyrneine B (2) were planned to be synthesized from C by means of 1,3-prototropic shift and γ-oxidation at C4, albeit numerous concerns such as stereo- as well as regio- and chemoselectivity are appreciably involved in these late-stage manipulations arising from the conjugation effect of multiple olefinic functionalities in the 5- and 7-membered ring, and the acidity of proton at C2 and C18. The intermediate A was proposed to be derived from the 5-6-6 tricyclic D by ring expansion. For the installation of the all-carbon quaternary stereocenter at the angular C6, we conceived of Birch reductive methylation from tricyclic ketone E. To our knowledge, such transformation has never been explored in the synthesis of cyathane-type natural products presumably due to the concerns of annular strain, steric hindrance, and stereoselectivity1,2,3. However, the great potential to streamline the synthesis of cyathane compounds prompted us to investigate it. The construction of the crucial tricyclic system F might be achieved through an intramolecular Friedel-Crafts reaction of aldehyde G whose synthesis would be implemented through the Suzuki-Miyaura cross-coupling of a heavily substituted nonactivated vinyl triflate H. Simplification of H revealed the five-membered cyclic ketone I, which was to be prepared through an enantioselective desymmetric reduction of 2,2-disubstituted 1,3-cyclopentanedione J.

Fig. 2

Retrosynthetic analysis of cyrneine A−B and glaucopine C. PG stands for protecting group; F–C represents Friedel–Crafts; unless otherwise noted, R in structures EJ indicates hydrogen or methyl group

Synthesis of cyrneine A

The synthesis commenced with asymmetric synthesis of the cyclopentenyl triflate 15a (Fig. 3). Accordingly, allylation of the readily available 2-methyl 1,3-cyclopentanedione 7 with allylic bromide 8 or 9 afforded 2,2-disubstituted cyclopentanedione 10 and 11 in high yields, respectively. Desymmetric enantioselective reduction of 10 and 11 was carried out by CBS reduction21,22. However, the result was less satisfactory in terms of enantio- and diastereoselectivity, and scalability. We then inspected the enzyme-catalyzed reduction with baker’s yeast23,24. Excellent enantioselectivity of up to 99% ee and moderate diastereoselectivity of ca. 8–9:1 were observed for 10. The imperfect diastereoselectivity prompted us to investigate the sterically more hindered 11. Delightedly, the d.r. ratio could be improved to ca. 25:1. Thus, a comparison of the results obtained from different ways showed that the enzyme-catalyzed reduction of prenyl substituted 11 afforded the best outcome. The reaction could be uneventfully performed on decagram scales to give α-hydroxyketone 12 in 65–68% yield with 99% ee and 25:1 d.r. (see Supplementary Fig. 36). Configuration inversion of the α-hydroxy group in 12 was carried out smoothly under Mitsunobu conditions to give the desired β-hydroxy intermediate 13. Protection of the β-hydroxy in 13 with TBS followed by a base-mediated isopropylation with iPrI provided ketone 14 in 80% yield over two steps (94% brsm). A literature survey showed that α-alkylation of ketone with secondary alkyl iodide was relatively difficult25,26. We examined the isopropylation under the effect of LDA, MHMDS (M = Li, Na, K), and NaH, respectively. The results showed that NaH was a more efficient base. Treatment of 14 with LiHMDS and PhNTf2 afforded the enol triflate 15a.

Fig. 3

Synthesis of 15a. Reagents and conditions: (a) 8 or 9 (2.0 equiv), K2CO3 (1.5 equiv), acetone, rt, overnight (75−80%); (b) Yeast extract (50 wt%), D-glucose, dry active baker’s yeast, H2O, rt, 36 h (67%); (c) p-NO2-C6H4CO2H (2.0 equiv), PPh3 (2.0 equiv), DEAD (2.0 equiv), THF, 0 to 50 °C, overnight (90%); (d) K2CO3 (2.0 equiv), MeOH/THF (v/v = 1:2), 0 oC, 30 min (98%); (e) TBSCl (1.2 equiv), imidazole (1.2 equiv), DMF, rt, overnight (91%); (f) NaH (5.0 equiv), iPrI (10.0 equiv), THF, reflux, overnight; then aq. HCl (2 M), rt, 1.5 h (88%); (g) LiHMDS (1.3 equiv, 1.0 M in THF), PhNTf2 (1.3 equiv), THF, −78 oC to rt, 3 h (80%). DEAD diethyl azodicarboxylate, TBSCl t-butyldimethylsilyl chloride, LiHMDS lithium hexamethyldisilazide, THF tetrahydrofuran, DMF N,N-dimethylformamide

The Suzuki-Miyaura cross-coupling involving sterically congested nonactivated enolate substrates was relatively rare. Initial scouting of the conditions for coupling triflate 15a with 16a was carried out by examining an array of conditions reported in literature27,28,29,30,31 (Table 1). Unfortunately, most of the reactions were less effective, affording the coupled product 17a in low yields (entries 1−6). While a combination of Pd(OAc)2 and dppb ligand could afford the product in moderate yield (entry 7), a large scale synthesis was problematic owing to an elongated reaction time, leading to partial hydrolysis of 15a. To compare with the prior literature27,28,29,30,31, the low coupling efficiency is probably due to the excessively congested structure of 15a with the additional presence of a bulky OTBS. To overcome this obstacle, we turned to examine the catalytic efficiency of phosphinamide-derived palladacycle 18, which was developed in our previous studies toward synthesizing P-stereogenic compounds through C–H arylation of phosphinamide32,33 and exhibited excellent catalytic activity for Suzuki cross-coupling of aryl (pseudo)halides under mild conditions34. To our delight, we found that the palladacycle 18 did display high catalytic activity for such a heavily substituted nonactivated triflate 15a. The coupled product 17a could be obtained in almost quantitative yield at room temperature (entry 8). Most significantly, the reaction could be reliably scaled up to multigram scales (6.6 g of 15a) without compromising the yield (entry 9).

Table 1 Suzuki–Miyaura cross-coupling of 15a and 16aa

To further expand the potential utility of the new precatalyst for mild and effective coupling of sterically hindered nonactivated enolate derivatives, we examined the substrate scope by varying the structures of both reaction partners. Effective cross-coupling was observed for an extensive combination of an array of heavily substituted nonactivated enol triflates and aryl boronic acids. As shown in Table 2, both the five-membered (17b17n) and six-membered (17o17r) cyclic enol triflates reacted smoothly with a rich range of aryl boronic acids whose structure was modified by electron-donating OMe, tBu, and Me, as well as electron-withdrawing F, 3,4,5-trifluoro, CF3, and CO2Me groups. In addition, a [2.2.1]-bridged bicycle (17s17w) also exhibited good compatibility. Notably, the reaction was viable for 2-furyl and benzo-2-furyl boronic acids (17f, 17j, 17n, 17r, and 17w). These results would be appealing because coupling of 2-heteroaryl boronic acids is a considerable challenge resulting from the detrimental pyrolysis under conventional heating conditions35, especially with the nonactivated enol triflates as seen from the sporadic examples explored in the synthesis of relevant natural products36.

Table 2 Scope of substratesa

Having established the robust conditions for large scale synthesis of 17a in this way, we then shifted our focus to construct the 5-6-6 tricarbocyclic system 23 (Fig. 4). Oxidation of the double bond in 17a delivered the aldehyde 19. For the Friedel-Crafts cyclization of 19, we first examined the acid-mediated protocols as investigated in Trost’s28 and Jiang’s37 synthesis of hamigeran B. However, similar to their outcome, the reaction proved to be futile owing to multiple difficulties associated with the poor regioselectivity of para vs. ortho to phenolic OH, the lability of OTBS group, and the ease of further dehydration of the cyclized product. After a careful deliberation, we devised a chelation-controlled strategy and found that EtMgBr was a suitable reagent. Namely, treatment of 19 with EtMgBr produced a magnesium phenolate salt. The Mg(II) ion may be acting to serve as a Lewis acid to coordinate with the aldehyde group, and thereby forming intermediate 20 through chelation-control. Consequently, the Friedel-Crafts reaction proceeded exclusively at the position ortho to phenolic OH to afford the tricyclic product 21. Upon in situ selective methylation of phenolic OH, the tricyclic alcohol 22 could be obtained as a single regioisomer in 64–72% yield on multigram scales. Oxidation of 22 gave the corresponding ketone 23 smoothly.

Fig. 4

Synthesis of the tricyclic compound 23. Reagents and conditions: (a) OsO4 (4 mol%), NaIO4 (5.0 equiv), pyridine (3.0 equiv), dioxane/H2O (v/v = 5:1), 80 °C (80%); (b) EtMgBr (1.1 eqiuv, 1.0 M in THF), −78 to 40 oC, overnight, then K2CO3 (2.0 equiv), MeI (5.0 equiv), and DMF were charged in situ, 55 oC, 10 h (72%); (c) PCC (4.0 equiv), NaOAc (4.0 equiv), celite (ca. 130 wt%), rt, 6 h (82%). THF tetrahydrofuran, DMF N,N-dimethylformamide, PCC pyridinium chlorochromate

Next, our task was moved forward to complete the synthesis of cyrneine A (1) (Fig. 5). Attempted installation of methyl group at C6 in 23 was carried out by executing the Birch reductive methylation. However, initial trials showed that the reaction was considerably challenging. Only a complex mixture was afforded under a broad array of conditions. Based on the NMR analysis of the crude products, the reaction was mainly complicated by the competitive reduction of C3 = C4 double bond, aryl ring, and carbonyl group without observation of the methylated product. After an exhaustive screening and optimization of conditions, we could successfully install the angular methyl group based on the methods reported early by Narisada38 and Gibbard39. It was found that addition of scrupulously dried LiBr was crucial. The desired product 24 could be obtained in 72–75% yield as a single diastereoisomer over gram scale. The exceptionally high stereoselectivity is presumably attributed to the steric hindrance of methyl group at C9, which compels the nucleophilic attack of TS-1 anion to MeI to take place from the less hindered si-face as illustrated by mode I versus mode II. The stereochemistry of 24 was determined by NOESY correlations (see Supplementary Fig. 21) and was further confirmed by X-ray single crystal analysis of the final product (vide infra).

Fig. 5

The completion of the synthesis of cyrneine A. Reagents and conditions: (a) Liq. NH3, tBuOH (1.0 equiv), K (2.5 equiv), Et2O, −78 °C, 10 min; then LiBr (2.5 equiv), MeI (5.0 equiv), and THF were charged in situ, −78 °C, 1 h, then warmed to rt over a period of 1 h (72%); (b) 25 (5.0 equiv), NaOAc (5.0 equiv), EtOH, 35 °C, 3 h; (c) KOtAm (5.0 equiv), degassed xylene, 140 °C, 1.8 h (36% for 26; 18% for 27); (d) TBSCl (1.2 equiv), imidazole (1.2 equiv), DMF, rt, overnight (93%); (e) 5% aq. HCl, THF, 15 to 20 oC, 40 min (89%); (f) LiHMDS (1 M in THF, 3.5 equiv), CNCO2Me (3.0 equiv), THF, −78 °C, 1 h; (g) ZnEt2 (1.0 M in hexane, 6.0 equiv), CH2I2 (6.0 equiv), CH2Cl2, rt, 2 h; I2 (7.0 equiv), rt; then saturated aq. Na2S2O3 (excess), rt; then DBU (20.0 equiv), rt, 10 min (73% for 2 steps); (h) TMSOTf (5.0 equiv), CH2Cl2, -25 oC, 15 min; (i) LiAlH4 (6.0 equiv), Et2O, 10 min at −78 °C, then warmed to rt; (j) MnO2 (50 equiv), CH2Cl2, rt, overnight (58% in 3 steps); tAm = tert-amyl; DBU = 1,8-diazabicyclo[5.4.0]undec-7-ene; TMSOTf = trimethylsilyl trifluoromethanesulfonate

Concerning the reduction of the carbonyl functionality in the central ring of 24, many unexpected obstacles were encountered. First, we examined the Barton-McCombie40 radical reduction involving reduction of the carbonyl group (NaBH4, MeOH), thiocarbonation of hydroxy (NaH, CS2, MeI), and radical induced deoxygenation. However, the product 26 was obtained in lower than 20% yield under a free combination of various radical initiators (e.g., AIBN, ABCN, Et3B,) and reductants (e.g., Bu3SnH, TMSH, TTMSS, and Ph2SiH2). Although no vigorous proof, it seemed that the cleavage of C6−C7 bond occurred facilely under radical conditions. Alternatively, the Wolff–Kishner–Huang type reduction was also proved to be ineffective under an array of routine conditions41,42,43,44,45,46,47,48. Extensive decomposition of substrate was observed. Fortunately, a patient investigation revealed that the reaction of 24 with semicarbazide 2549,50 followed by treatment of the resulting semicarbazone with KOtAm in degassed xylene afforded 26 in ca. 36% yield accompanied by ca. 18% of desilylated 27, which could be resilylated to give 26. As a result, 26 could be obtained in 53% yield in a synthetically useful level. Hydrolysis of the vinyl ether in 26 gave ketone 28, which was immediately subjected to the ring expansion reaction without careful purification since 28 was somewhat easily oxidized under ambient atmosphere. For ring expansion, Nakada in the synthesis of allocyathin B22 employed a four-step sequence involving acylation, iodomethylation, SmI2-promoted ring expansion, and LDA/I2-meidated elimination. Inspired by a protocol of Zercher51, we accomplished the conversions through a two-step operation involving acylation followed by a one-pot Zn carbenoid-mediated ring expansion and I2-promoted elimination. Compound 29 was thus obtained efficiently in 73% yield over two steps. Finally, elaboration of 29 by removal of TBS, simultaneous reduction of ketone and ester, and selective oxidation of allylic primary alcohol furnished the total synthesis of cyrneine A (1) in 58% yield over three steps. Notably, the reduction proceeded highly stereoselectively at C14 to afford β-OH product. The structure of 1 was unambiguously confirmed by 1H- and 13C-NMR, HRMS, and single crystal X-ray (CCDC 1830226) analysis. The data and dextrorotary property of the final product matched well with those of the reported natural sample16 (See Supplementary Table 1 and 2, and Supplementary Fig. 26).

Synthesis of cyrneine B and glaucopine C

Having successfully synthesized cyrneine A, we entered the final stage toward synthesizing cyrneine B (2) and glaucopine C (3) (Fig. 6). Based on our retrosynthetic design, the advanced intermediate 29 was converted into β,γ-enone 30 through four routine transformations. After an optimization of reaction sequence and conditions, we found that the 1,3-prototropic shift and concomitant deprotection of acetyl in 30 proceeded smoothly under the effect of NaOMe to deliver the thermodynamically preferred enone 31 as a single C4 β-H stereoisomer. The stereochemistry was determined by NOESY correlation (see Supplementary Fig. 29). The exceptionally good stereoselectivity is presumably resulted from the differential steric hindrance between re-face and si-face of TS-2. As a result, the enolate anion prefers to approach the electrophiles from the less congested si-face rather than the hindered re-face (i.e., mode III vs. IV). Subsequently, selective oxidation of the allylic primary alcohol completed the synthesis of glaucopine C (3). Encouraged by the highly stereo- and regioselective prototropic shift, the installation of C4 β-hydroxy toward synthesizing cyrneine B (2) was carried out though a base-mediated prototropic shift and aerobic γ-CH oxidation cascade from 30. While a complex mixture with high polarity was obtained in initial scouting of the conditions under the effect of weak bases and heating presumably due to over oxidation of olefins and acidic CH at C2 and C18, treatment of 30 with LiHMDS by lowering the temperature to –78 °C under O2 atmosphere afforded 32 in 58% yield. Finally, removal of acetyl followed by selective oxidation of the allylic alcohol delivered cyrneine B (2). The structures of cyrneine B and glaucopine C were confirmed by various spectroscopic analyses and by comparison of the analytical data of the synthetic samples with those reported for natural products16,19 (see Supplementary Table 36, and Supplementary Fig. 3035).

Fig. 6

The synthesis of cyrneine B and glaucopine C. Reagents and conditions: (a) LiAlH4 (6.0 equiv), Et2O, 20 min at −78 °C, then warmed to rt; (b) Ac2O (15.0 equiv), DMAP (20 mol%), pyridine, 30 min, rt; (c) HF•Py (excess), THF, rt, 2 h; (d) DMP (1.6 equiv), CH2Cl2, 30 min, rt (52% for 4 steps); (e) NaOMe, MeOH, 35 °C, 4 h (73%); (f) MnO2 (15 equiv), CH2Cl2, rt, 3 h (82%); (g) LiHMDS (2.0 equiv), THF, −78 °C, 15 min, then P(OMe)3 (4.0 equiv), O2, 2 h (58%); (h) K2CO3 (excess), MeOH, 35 °C, 4 h (51% for 2 steps). DMAP 4-(dimethylamino)pyridine, Py pyridine, DMP Dess–Martin periodinane


In summary, we have developed an efficient route that allowed for a more step-economic total synthesis of cyrneine A (20 steps), and the first total synthesis of cyrneine B (24 steps) and glaucopine C (23 steps) from readily available commercial materials. The synthesis features the use of a mild and efficient Suzuki-coupling of heavily substituted nonactivated vinyl triflate, a Mg(II)-mediated chelation-controlled Friedel–Crafts cyclization, a Birch reductive methylation, and a zinc carbenoid-mediated ring expansion. These key transformations enable an efficient and rapid construction of the 5-6-7 tricyclic core. Finally, the divergent synthesis of the three natural products from this core is achieved through several carefully orchestrated manipulations involving a stereoselective reduction of C14 carbonyl, a stereoselective 1,3-prototropic shift, and a stereo- and chemoselective prototropic shift/γ-CH oxidation cascade at C4. The utility of the new strategy and methods for efficient and flexible synthesis of other structurally relevant products is currently underway.


Procedures for the synthesis of cyrneines A–B and glaucopine C

The detailed experimental procedures for the synthesis of cyrneines A, B, and glaucopine C were provided in Supplementary Information.

General procedure for the cross-coupling reaction of enol triflates

To a solution of vinyl triflate 15 (0.2 mmol) in a mixed solvent of DMF (1.0 mL) and EtOH (1.0 mL) was added arylboronic acid 16 (0.4 mmol, 2.0 equiv), palladacycle 18 (5.6 mg, 5 mmol%), and K3PO4 [127 mg, 0.6 mmol, 3.0 equiv (K2CO3 was used for the coupling of 15a with 16a)] at room temperature under nitrogen atmosphere. The resulting mixture was stirred at the same temperature until the vinyl triflate had disappeared as monitored by TLC. The reaction mixture was then poured into water and extracted with ethyl acetate (3 × 25 mL). The organic layer was combined, washed with brine, dried over Na2SO4, and concentrated under vacuum. The residue was purified by silica gel column chromatography to afford the desired cross-coupling product 17.

Data availability

Chemical compound information including NMR and HRMS data, copies of 1H- and 13C-NMR of all new compounds, 2D NMR of compounds 24, 31, cyrneine B (2), and glaucopine (3), HPLC charts for compound 12, and single X-ray crystal data of cyrneine A (1). This material is provided in Supplementary Information. The X-ray crystallographic coordinates for cyrneine A (1) reported in this study have also been deposited at the Cambridge Crystallographic Data Centre (CCDC), under deposition number 1830226. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via Other supporting data related to this work are available from the corresponding author upon reasonable request.


  1. 1.

    Enquist, J. A. Jr & Stoltz, B. M. Synthetic efforts toward cyathane diterpenoid natural products. Nat. Prod. Rep. 26, 661–680 (2009).

    Article  PubMed  PubMed Central  CAS  Google Scholar 

  2. 2.

    Nakada, M. Enantioselective total synthesis of cyathane diterpenoids. Chem. Rec. 14, 641–662 (2014).

    Article  PubMed  CAS  Google Scholar 

  3. 3.

    Tang, H.-Y., Yin, X., Zhang, C.-C., Jia, Q. & Gao, J.-M. Structure diversity, synthesis, and biological activity of cyathane diterpenoids in higher fungi. Curr. Med. Chem. 22, 2375–2391 (2015).

    Article  PubMed  CAS  Google Scholar 

  4. 4.

    Ward, D. E., Gai, Y. & Qiao, Q. A general approach to cyathin diterpenoids. Total synthesis of allocyathin B3. Org. Lett. 2, 2125–2127 (2000).

    Article  PubMed  CAS  Google Scholar 

  5. 5.

    Ward, D. E. & Shen, J. Enantioselective total synthesis of cyathin A3. Org. Lett. 9, 2843–2846 (2007).

    Article  PubMed  CAS  Google Scholar 

  6. 6.

    Trost, B. M., Dong, L. & Schroeder, G. M. Total synthesis of ( + )-allocyathin B2. J. Am. Chem. Soc. 127, 2844–2845 (2005).

    Article  PubMed  CAS  Google Scholar 

  7. 7.

    Trost, B. M., Dong, L. & Schroeder, G. M. Exploiting the Pd- and Ru-catalyzed cycloisomerizations: enantioselective total synthesis of ( + )-allocyathin B2. J. Am. Chem. Soc. 127, 10259–10268 (2005).

    Article  PubMed  PubMed Central  CAS  Google Scholar 

  8. 8.

    Waters, S. P., Tian, Y., Li, Y.-M. & Danishefsky, S. J. Total synthesis of (−)-scabronine G, an inducer of neurotrophic factor production. J. Am. Chem. Soc. 127, 13514–13515 (2005).

    Article  PubMed  CAS  Google Scholar 

  9. 9.

    Enquist, J. A. Jr & Stoltz, B. M. The total synthesis of (−)-cyanthiwigin F by means of double catalytic enantioselective alkylation. Nature 453, 1228–1231 (2008).

    ADS  Article  PubMed  PubMed Central  CAS  Google Scholar 

  10. 10.

    Pfeiffer, M. W. B. & Phillips, A. J. Total synthesis of ( + )-cyanthiwigin U. J. Am. Chem. Soc. 127, 5334–5335 (2005).

    Article  PubMed  CAS  Google Scholar 

  11. 11.

    Reddy, T. J., Bordeau, G. & Trimble, L. Total synthesis of ( + )-cyanthiwigin AC. Org. Lett. 8, 5585–5588 (2006).

    Article  PubMed  CAS  Google Scholar 

  12. 12.

    Snider, B. B., Vo, N. H., O’Neil, S. V. & Foxman, B. M. Synthesis of ( ± )-allocyathin B2 and ( + )-erinacine A. J. Am. Chem. Soc. 118, 7644–7645 (1996).

    Article  CAS  Google Scholar 

  13. 13.

    Snider, B. B., Vo, N. H. & O’Neil, S. V. Synthesis of ( ± )-allocyathin B2 and ( + )-erinacine A. J. Org. Chem. 63, 4732–4740 (1998).

    Article  CAS  Google Scholar 

  14. 14.

    Tori, M., Toyoda, N. & Sono, M. Total synthesis of allothathin B2, a metabolite of bird’s nest fungi. J. Org. Chem. 63, 306–313 (1998).

    Article  CAS  Google Scholar 

  15. 15.

    Piers, E., Gilbert, M. & Cook, K. L. Total synthesis of the cyathane diterpenoid ( ± )-sarcodonin G. Org. Lett. 2, 1407–1410 (2000).

    Article  PubMed  CAS  Google Scholar 

  16. 16.

    Marcotullio, M. C., Pagiotti, R. & Maltese, F. et al. Neurite outgrowth activity of cyathane diterpenes from Sarcodon cyrneus, cyrneine A and B. Planta Med. 72, 819–823 (2006).

    Article  PubMed  CAS  Google Scholar 

  17. 17.

    Marcotullio, M. C., Pagiotti, R. & Maltese, F. et al. Cyathane diterpenes from Sarcodon cyrneus and evaluation of their activities of neuritegenesis and nerve growth factor production. Bioorg. Med. Chem. 15, 2878–2882 (2007).

    Article  PubMed  CAS  Google Scholar 

  18. 18.

    Obara, Y., Hoshino, T., Marcotullio, M. C., Pagiotti, R. & Nakahata, N. A novel cyathane diterpene, cyrneine A, induces neurite outgrowth in a Rac1-dependent mechanism in PC12 cells. Life Sci. 80, 1669–1677 (2007).

    Article  PubMed  CAS  Google Scholar 

  19. 19.

    Marcotullio, M. C., Pagiotti, R. & Campagna, V. et al. Glaucopine C, a new diterpene from the fruiting bodies of Sarcodon glaucopus. Nat. Prod. Res. 20, 917–921 (2006).

    Article  PubMed  CAS  Google Scholar 

  20. 20.

    Elamparuthi, E., Fellay, C., Neuburger, M. & Gademann, K. Total synthesis of cyrneine A. Angew. Chem. Int. Ed. 51, 4071–4073 (2012).

    Article  CAS  Google Scholar 

  21. 21.

    Shimizu, M., Yamada, S., Fujita, Y. & Kobayashi, F. Highly stereocontrolled reduction of 1,3-cyclopentanediones using oxazaborolidine-BH3. Tetrahedron.: Asymmetry 11, 3883–3886 (2000).

    Article  CAS  Google Scholar 

  22. 22.

    Liu, L. L. & Chiu, P. An expeditious asymmetric synthesis of the pentacyclic core of the cortistatins by an intramolecular (4 + 3) cycloaddition. Chem. Commun. 47, 3416–3417 (2011).

    Article  CAS  Google Scholar 

  23. 23.

    Csuk, R. & Glaenzer, B. I. Baker’s yeast mediated transformations in organic chemistry. Chem. Rev. 91, 49–97 (1991).

    Article  CAS  Google Scholar 

  24. 24.

    Brooks, D. W., Mazdiyasni, H. & Grothaus, P. G. Asymmetric microbial reduction of prochiral 2,2-disubstituted cycloalkanediones. J. Org. Chem. 52, 3223–3232 (1987).

    Article  CAS  Google Scholar 

  25. 25.

    Kraft, P. & Popaj, K. New musk odorants: (3E)-4-(2′-alkyl-5′,5′-dimethylcyclopent-1′-enyl)but-3-en-2-ones and (3E)-1-acetyl-3-alkylidene-4,4-dimethylcyclohexenes. Eur. J. Org. Chem. 4806–4814 (2008).

  26. 26.

    Cornella, J., Jackson, E. P. & Martin, R. Nickel-catalyzed enantioselective C−C bond formation through Csp 2−O cleavage in aryl esters. Angew. Chem. Int. Ed. 54, 4075–4078 (2015).

    Article  CAS  Google Scholar 

  27. 27.

    Willis, M. C., Claverie, C. K. & Mahon, M. F. Tandem intermolecular Suzuki coupling/intramolecular vinyl triflate-aryl coupling. Chem. Commun. 0, 832–833 (2002).

  28. 28.

    Trost, B. M., Pissot-Soldermann, C. & Chen, I. A short and concise synthesis of hamigeran B. Chem. Eur. J. 11, 951–959 (2005).

    Article  PubMed  CAS  Google Scholar 

  29. 29.

    Occhiato, E. G., Galbo, F. L. & Guarna, A. Preparation and Suzuki-Miyaura coupling reactions of tetrohydropyridine-2-boronic acid pinacol esters. J. Org. Chem. 70, 7324–7330 (2005).

    Article  PubMed  CAS  Google Scholar 

  30. 30.

    Baxter, J. M., Steinhuebel, D., Palucki, M. & Davies, I. W. Stereoselective enol tosylation: preparation of trisubstituted α,β-unsaturated esters. Org. Lett. 7, 215–218 (2005).

    Article  PubMed  CAS  Google Scholar 

  31. 31.

    Li, X., Xue, D., Wang, C. & Gao, S. Total synthesis of the hamigerans. Angew. Chem. Int. Ed. 55, 9942–9946 (2016).

    Article  CAS  Google Scholar 

  32. 32.

    Du, Z.-J., Guan, J., Wu, G.-J., Xu, P., Gao, L.-X. & Han, F.-S. Pd(II)-catalyzed enantioselective synthesis of P-stereogenic phosphinamides via desymmetric C−H arylation. J. Am. Chem. Soc. 137, 632–635 (2015).

    Article  PubMed  CAS  Google Scholar 

  33. 33.

    Guan, J., Wu, G.-J. & Han, F.-S. PdII-catalyzed mild C−H ortho arylation and intramolecular amination oriented by a phosphinamide group. Chem. Eur. J. 20, 3301–3305 (2014).

    Article  PubMed  CAS  Google Scholar 

  34. 34.

    Wu, G.-J., Han, F.-S. & Zhao, Y.-L. Palladacycles derived from arylphosphinamides for mild Suzuki–Miyaura cross-couplings. RSC Adv. 5, 69776–69781 (2015).

    Article  CAS  Google Scholar 

  35. 35.

    Kinzel, T., Zhang, Y. & Buchwald, S. L. A new palladium precatalyst allows for the fast Suzuki-Miyaura coupling reactions of unstable polyfluorophenyl and 2-heteroaryl boronic acids. J. Am. Chem. Soc. 132, 14073–14075 (2010).

    Article  PubMed  PubMed Central  CAS  Google Scholar 

  36. 36.

    Kuang, L., Liu, L. L. & Chiu, P. Formal total synthesis of ( + )-cortistatins A and J. Chem. Eur. J. 21, 14287–14291 (2015).

    Article  PubMed  CAS  Google Scholar 

  37. 37.

    Jiang, B., Li, M.-M., Xing, P. & Huang, Z.-G. A concise formal synthesis of (−)-hamigeran B. Org. Lett. 15, 871–873 (2013).

    Article  PubMed  CAS  Google Scholar 

  38. 38.

    Narisada, M. & Watanabe, F. Reductive alkylation of monoaromatic ketones. J. Org. Chem. 38, 3887–3892 (1973).

    Article  CAS  Google Scholar 

  39. 39.

    Gibbard, H. C., Moody, C. J. & Rees, C. W. 3aH-indenes. Part 5. Preparation and reactions of 3-methoxy- and 3-trimethylsiloxy-3a-substituted-3aH-indenes. J. Chem. Soc. Perkin Trans. 1, 0, 723–729 (1985).

  40. 40.

    Crich, D. & Quintero, L. Radical chemistry associated with the thiocarbonyl group. Chem. Rev. 89, 1413–1432 (1989).

    Article  CAS  Google Scholar 

  41. 41.

    Toyota, M., Wada, T. & Ihara, M. Total synthesis of (−)-methyl atis-16-en-19-oate, (−)-methyl kau-16-en-19-oate, and (−)-methyl trachyloban-19-oate by a combination of palladium-catalyzed cycloalkenylation and homoallyl-homoallyl radical rearrangement. J. Org. Chem. 65, 4565–4570 (2000).

    Article  PubMed  CAS  Google Scholar 

  42. 42.

    Marino, J. P., Rubio, M. B., Cao, G. & de Dios, A. Total synthesis of ( + )-aspidospermidine: a new strategy for the enantiospecific synthesis of aspidosperma alkaloids. J. Am. Chem. Soc. 124, 13398–13399 (2002).

    Article  PubMed  CAS  Google Scholar 

  43. 43.

    Peterli-Roth, P., Maguire, M. P., León, E. & Rapoport, H. Synthesis of 6-deaminosinefungin and (S)-6-methyl-6-deaminosinefungin. J. Org. Chem. 59, 4186–4193 (1994).

    Article  CAS  Google Scholar 

  44. 44.

    Hutchins, R. O., Milewski, C. A. & Maryanoff, B. E. Selective deoxygenation of ketones and aldehydes including hindered systems with sodium cyanoborohydride. J. Am. Chem. Soc. 95, 3662–3668 (1973).

    Article  CAS  Google Scholar 

  45. 45.

    Thompson, C. F., Jamison, T. F. & Jacobsen, E. N. Total synthesis of FR901464. Convergent assembly of chiral components prepared by asymmetric catalysis. J. Am. Chem. Soc. 122, 10482–10483 (2000).

    Article  CAS  Google Scholar 

  46. 46.

    Klahn, P., Duschek, A., Liébert, C. & Kirsch, S. F. Total synthesis of ( + )-cyperolone. Org. Lett. 14, 1250–1253 (2012).

    Article  PubMed  CAS  Google Scholar 

  47. 47.

    Paquette, L. A., Wang, T.-Z. & Vo, N. H. Access to naturally occurring cyclooctanoids by two-carbon intercalation. Total synthesis of ( + )-ceroplastol I. J. Am. Chem. Soc. 115, 1676–1683 (1993).

    Article  CAS  Google Scholar 

  48. 48.

    Hayashida, J. & Rawal, V. H. Total synthesis of ( ± )-platencin. Angew. Chem. Int. Ed. 47, 4373–4376 (2008).

    Article  CAS  Google Scholar 

  49. 49.

    Nakajima, R., Ogino, T., Yokoshima, S. & Fukuyama, T. Total synthesis of (−)-mersicarpine. J. Am. Chem. Soc. 132, 1236–1237 (2010).

    Article  PubMed  CAS  Google Scholar 

  50. 50.

    Grundon, M. F., Henbest, H. B. & Scott, M. D. The reactions of hydrazones and related compounds with strong bases. Part I. A modified Wolff-Kishner procedure. J. Chem. Soc. 0, 1855–1858 (1963).

  51. 51.

    Lin, W. & Zercher, C. K. Formal synthesis of ( + )-brefeldin A: application of a zinc-mediated ring expansion reaction. J. Org. Chem. 72, 4390–4395 (2007).

    Article  PubMed  PubMed Central  CAS  Google Scholar 

Download references


We thank Prof. Bao-Min Wang at Dalian University of Technology for helpful discussions on the revision of the manuscript. Financial support from NSFC (21572215, 21602215), and State Key Laboratory of Fine Chemicals (KF 1515) is acknowledged.

Author information




F.S.H. conceived the synthetic strategy, directed the project, and wrote the manuscript. F.S.H. and G.J.W. analyzed the experiment results. G.J.W., Y.H.Z. and D.X.T. conducted the experimental work.

Corresponding author

Correspondence to Fu-She Han.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Publisher's note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Electronic supplementary material

Rights and permissions

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Wu, G., Zhang, Y., Tan, D. et al. Total synthesis of cyrneines A–B and glaucopine C. Nat Commun 9, 2148 (2018).

Download citation

Further reading


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.


Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing