[C:1]([CH:5]1[CH2:15][CH2:14][C:8]2([O:12][CH2:11][C:10](=[O:13])[CH2:9]2)[CH2:7][CH2:6]1)([CH3:4])([CH3:3])[CH3:2].[BH4-].[Na+].[H][H]>CO>[C:1]([CH:5]1[CH2:15][CH2:14][C:8]2([O:12][CH2:11][CH:10]([OH:13])[CH2:9]2)[CH2:7][CH2:6]1)([CH3:4])([CH3:2])[CH3:3]To an ice cooled solution of 8-t-butyl-1-oxaspiro(4,5)decane-3-one (44.1 g, 0.21 mmol) in methanol (300 ml) was added sodium borohydride (10.8 g, 0.285 mol) in portions. After the evolution of hydrogen ceased the cooling bath was removed and the mixture was stirred at room temperature over night. The solvent was evaporated in vacuo and the residue was taken up in toluene/diluted hydrochloric acid. The organic layer was washed twice with water (200 ml), dried (MgSO4) and evaporated in vacuo to yield a colourless oil (44 g) which was recrystallised from light petroleum. 30 g of colourless crystals were obtained which melted at 82°-84° C. TLC and NMR-analysis indicated a single diastereoisomer only (cis).
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