Patent ID: 6852880

Claim:
A process for preparing a compound of the following formula (1): in which R 1 represents H or C 1 -C 5 -alkyl, X represents CH 2 , O, or S, and R′ represents C 2 -C 4 -alkyl; phenyl optionally substituted by halogen, C 1 -C 5 -alkyl, C 1 -C 4 -alkoxy, CF 3 , C 1 -C 3 -aliphatic acylamino; 5- or 6-membered heterocycle containing one or more hetero atoms selected from a group consisting of nitrogen, oxygen and sulfur; C 3 -C 7 -cycloalkyl; or C 3 -C 7 -cycloalkenyl, which comprises the first step wherein an alkyl halide containing 15S-alcohol of the following formula (3): in which X and R′ are defined as above, Y represents a leaving group, and R″ represents a hydroxy-protecting group, is converted into a cuprate thereof and the cuprate compound is subjected to a stereoselective 1,4-addition reaction to an α,β-unsaturated ketone compound of the following formula (2): in which R 1 is defined as above, and R 2 represents a hydroxy-protecting group, to give a compound of the following formula (4): in which X, R′, R″, R 1 and R 2 are defined as above; the second step wherein the ketone group on the cyclopentanone ring of the compound of formula (4) is reduced using a metal hydride to give an α-alcohol compound of the following formula (5): in which X, R′, R″, R 1 and R 2 are defined as above; and the third step wherein the alcohol protecting groups on the cyclopentanone ring and ω-chain in the compound of formula (5) are removed to give the compound of formula (1).