To a -50° C. solution of 12.1 g (25.1 mmol) of N-ethoxycarbonyl-2-[2-benzyloxy-4-(1,1-dimethylheptyl)phenyl]-4-piperidinone in 90 ml methanol and 90 ml of tetrahydrofuran is added 1.04 g (27.5 mmole) of sodium borohydride. The reaction is stirred 2 hours at -50° C. and then allowed to warm to 25° C. The reaction is quenched by addition to 300 ml saturated sodium chloride and the mixture extracted with ethyl ether (2 liters). The organic extract is washed with 300 ml saturated sodium chloride, dried over magnesium sulfate and the ether evaporated in vacuo. The crude product is purified via column chromatography on 2 kg silica gel eluting in 500 ml fractions with 2% methanol-5% ether-93% dichloromethane to yield (fractions 20-26) 6.04 g (50%) of the title compound as an oil and 3.75 g (31% of a mixture of the title compound and its trans-isomer. Further chromatography yields pure trans-isomer.
