Compound 28
(2S,2'R,3a'S,4'S,8'S,13a'S)-13a'-(((2S,4R,5S,6S)-5-Acetyl-4,5-dihydroxy-6-methyltetrahydro-2H-pyran-2-yl)oxy)-8'-(benzyloxy)-2'-(dimethoxymethyl)-12'-hydroxy-7'-methoxy-5'-methyl-3a',4',8',9',10',13a'-hexahydro-2'H,11'H-spiro[oxirane-2,1'-[2,4]epoxyfuro[3,2-b]naphtho[2,3-h]chromen]-11'-one
From: Component-based syntheses of trioxacarcin A, DC-45-A1 and structural analogues
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InChIKey QSWUSWBBPAAYDY-CPEWZHLBSA-N
Synthetic procedure: See article for the definitive version of this procedure and for full experimental details.
Potassium carbonate (0.3 mg, 2 μmol, 0.3 equiv) was added to an ice-cooled solution of α-glycoside 54 (5 mg, 6 μmol, 1 equiv) in methanol (1.0 mL). After 30 min, the cooling bath was removed and the reaction flask was allowed to warm to 23 °C. After 2 h, the mixture was partitioned between chloroform (40 mL) and saturated aqueous sodium chloride solution (10 mL). The layers were separated. The aqueous layer was extracted with chloroform (3 × 20 mL). The organic layers were combined and the combined solution was dried over sodium sulfate. The dried solution was filtered and the filtrate was concentrated. The residue was purified by preparatory HPLC (Agilent Prep-C18 column, 10 μm, 30 × 150 mm, UV detection at 270 nm, gradient elution with 40→90% acetonitrile in water, flow rate: 15 mL/min) to provide after concentration the pure diol 28 (3 mg, 63%, in fractions eluting at 28–30 min) as a yellow solid. TLC: (67% ethyl acetate−hexanes) Rf = 0.32 (UV, CAM); 1H NMR (500 MHz, CDCl3) δ: 14.76 (s, 1H), 7.52 (s, 1H), 7.36–7.28 (m, 5H), 5.86 (br d, 1H, J = 2.3 Hz), 5.34 (d, 1H, J = 4.4 Hz), 5.24 (d, 1H, J = 4.4 Hz), 5.17 (br s, 1H), 5.02 (q, 1H, J = 6.3 Hz), 4.76 (s, 1H), 4.7 (d, 1H, J = 11.5 Hz), 4.58 (d, 1H, J = 11.5 Hz), 4.26 (d, 1H, J = 9.5 Hz), 4.15 (s, 1H), 3.82 (s, 3H), 3.71 (d, 1H, J = 9.5 Hz), 3.63 (s, 3H), 3.49 (s, 3H), 3.2 (ddd, 1H, J = 18.1, 13.6, 5.2 Hz), 2.97 (d, 1H, J = 5.6 Hz), 2.9 (d, 1H, J = 5.9 Hz), 2.61 (s, 3H), 2.60–2.51 (m, 2H), 2.49 (s, 3H), 2.43 (dt, 1H, J = 14.5, 3.3 Hz), 2.12 (d, 1H, J = 14.7 Hz), 2.06 (tdd, 1H, J = 13.5, 4.0, 1.6 Hz), 1.09 (d, 3H, J = 6.3 Hz); 13C NMR (125 MHz, CDCl3) δ: 210.5, 204.3, 163.0, 151.6, 143.8, 141.8, 138.2, 135.2, 128.4, 128.3, 127.8, 127.7, 116.7, 114.7, 114.1, 109.7, 104.6, 101.4, 99.7, 94.8, 79.6, 71.5, 70.6, 70.3, 69.3, 68.3, 67.7, 63.8, 62.8, 56.8, 56.1, 48.2, 32.4, 31.5, 27.8, 26.5, 20.3, 14.5; FTIR (neat), cm–1: 3512 (br w), 2926 (m), 1621 (s), 1389 (s), 1084 (s), 984 (s); HRMS (ESI): Calcd for (C40H44O15 + Na)+: 787.2572, Found: 787.2571.
