To a solution of 4.62 g (9.59 mmole) of N-ethoxycarbonyl-cis-2-[2-benzyloxy-4-(1,1-dimethylheptyl)phenyl]-4-piperidinol in 5 ml ethanol is added a solution of 4.2 g (75 mmole) of potassium hydroxide in 25 ml ethylene glycol and 4.2 ml water. The resultant mixture is evaporated at reduced pressure to remove ethanol and is then heated to reflux (bath 185° C.). After 24 hours material boiling at 80°-100° C. is removed by distillation, 6 ml ethylene glycol is added and the reaction continued at reflux for 17 hours. After cooling, the mixture is added to 500 ml dichloromethane and 80 ml water. The organic extract is washed with 80 ml saturated sodium chloride, dried over magnesium sulfate and evaporated in vacuo. The resulting crude oil is purified via column chromatography on 300 g of silica gel eluting in 20 ml fractions with 2.5% triethylamine, 2.5% methanol, 95% ethyl ether (fractions 1-109) and 5% triethylamine, 5% methanol, 90% ethyl ether (fractions 110-200). Fractions 138-190 gave 3.13 g (83%) of the title compound.
