[O:1]=[O+][O-].[CH2:4]([O:6][C:7]([C@@H:9]1[CH2:13][CH2:12][CH:11]([CH2:14][CH:15]=C)[N:10]1[C:17]([O:19][C:20]([CH3:23])([CH3:22])[CH3:21])=[O:18])=[O:8])[CH3:5].[BH4-].[Na+]>CO.C(Cl)Cl>[CH2:4]([O:6][C:7]([C@@H:9]1[CH2:13][CH2:12][CH:11]([CH2:14][CH2:15][OH:1])[N:10]1[C:17]([O:19][C:20]([CH3:23])([CH3:22])[CH3:21])=[O:18])=[O:8])[CH3:5]Ozone was passed at −78° C. through a solution of 1.00 g of 169 (3.53 mmol) in a mixture of 12 ml of MeOH and 6 ml of CH2Cl2 until the solution turned blue. The reaction was subsequently terminated and excess ozone removed by purging with oxygen. Thereafter, 270 mg of NaBH4 (7.06 mmol, 2 eq.) was added and the mixture stirred overnight to allow warming to RT. After checking completion of the reaction by means of TLC (EE/CH 1:1), the batch was concentrated and the remaining residue taken up in 60 ml of CH2Cl2 and 40 ml of half-conc. NaCl solution. The aqueous phase was extracted with 3×20 ml of CH2Cl2, the combined organic phases were dried over MgSO4 and concentrated. The residue was purified using silica gel column chromatography (EEICH 1:1) to obtain 691 mg (2.40 mmol, 68%) of alcohol 170 as a mixture of epimers (colorless oil).
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