[CH3:1][C:2]([C:5]1[CH:6]=[C:7]([CH2:15][CH:16]2[CH2:20][CH2:19][CH2:18][C:17]2=[O:21])[CH:8]=[C:9]([C:11]([CH3:14])([CH3:13])[CH3:12])[CH:10]=1)([CH3:4])[CH3:3].[BH4-].[Na+].C(O)(=O)C>C(O)C.O>[CH3:4][C:2]([C:5]1[CH:6]=[C:7]([CH2:15][C@H:16]2[CH2:20][CH2:19][CH2:18][C@H:17]2[OH:21])[CH:8]=[C:9]([C:11]([CH3:12])([CH3:13])[CH3:14])[CH:10]=1)([CH3:1])[CH3:3]To a solution of 710 mg (2.48 mmoles) of the title product of Example 5 in 25 ml of ethanol was added dropwise a solution of 188 mg (4.97 mmoles) of sodium borohydride in 3 ml of water. After 30 minutes, acetic acid was added, most of the ethanol was evaporated, the residue was partitioned between diethyl ether and dilute aqueous hydrochloric acid, the aqueous layer was further extracted with ether, and the combined organic extracts were washed with brine, dried over sodium sulfate, filtered, and evaporated. Chromatography of the residue using 15% ethyl acetate/hexane as eluent gave the title cis isomer (105 mg) and the title trans isomer (155 mg) as colorless oils. The structures were supported by 1H NMR.
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