Reaction Steps
A solution of the ester 19 (3.8 g, 8.83 mmol, 1.0 equiv.) in THF (100 mL) was cooled to 0° C. and treated with LiBH4 (0.29 g, 13.25 mmol, 1.5 equiv.) in portions. After stirring for 30 min at 0° C., the reaction mixture was allowed to warm to room temperature and stirred under a nitrogen atmosphere for 4 h at which time TLC (SiO2, EtOAc) revealed complete consumption of ester 19. The mixture was cooled to 0° C. again and water (100 mL) was carefully added followed by 1N HCl (250 mL) which provoked vigorous effervescence. After evaporation of the THF in vacuo, the mixture was neutralised to pH 7 with 1N NaOH. The aqueous solution was then extracted with EtOAc (4×70 mL), the combined organic layers washed with brine (50 mL), dried (MgSO4), filtered and evaporated in vacuo to furnished the pure diol 20 (3.2 g, 7.96 mmol, 90%), which was used in the subsequent reaction without further purification. [α]29D=−96° (c=0.15, CHCl3); 1H NMR (CDCl3, 400 MHz): δ 1.85-1.99 (m, 1H, 1-H), 2.09-2.28 (m, 1H, 1-H), 3.11-3.20 (m, 1H, 11-H), 3.25-3.39 (m, 1H, 11-H), 3.70-3.82 (m, 1H, 3-H), 3.85-4.04 (m, 5H, 3-H, 7-OMe, OH), 4.30-4.38 (m, 1H, 11a-H), 4.46-4.61 (m, 2H, 2-H), 5.20 (m, 2H, OCH2Ph), 6.86 (s, 1H, 6-H), 7.29-7.50 (m, 5H, Ph), 7.74 (s, 1H, 9-H); 13C NMR (CDCl3, 100 MHz): δ 37.1, 56.8, 56.9, 59.9, 65.0, 69.4, 71.4, 109.1, 109.3, 127.6, 127.7, 128.5, 128.8, 135.2, 137.2, 148.2, 155; IR (neat): 3357, 2938, 1614, 1576, 1520, 1454, 1434, 1333, 1276, 1220, 1069, 1048, 1006, 730, 698, 647 cm−1; MS (ES+) m/z (relative intensity) 426 ([M+Na]+., 5), 403 ([M+H]+., 100), 404 ([M+2H]+., 40).
