Patent ID: 7345181

Claim:
A process for preparing a compound of the following formula: wherein R 1 represents a cation, H, or C 1-12 alkyl, R 2 and R 3 each represent H or a hydroxy protective group, R 4 represents H or C 1-3 alkyl, and R 5 represents H or C 1-6 alkyl, comprising the steps of: (1) converting a compound of the following formula: wherein R 3a represents a hydroxy protective group, and R 4 and R 5 are each as defined above, into its cuprate, and then, performing stereo-specific 1,4-addition reaction of the cuprate to an α, β-unsaturated ketone of the following formula: wherein R 1 is as defined above, R 2a represents a hydroxy protective group, and R′ represents a hydroxy protective group, to form a compound of the following formula; wherein R 1 , R 2a , R 3a , R 4 , R 5 and R′ are each as defined above; (2) reducing a ketone of cyclopentanone in the compound of formula (IV) to form an α-alcohol compound of the following formula: wherein R 1 , R 2a , R 3a , R 4 , R 5 , and R′ are each as defined above; (3) substituting the α-alcohol of the compound of formula (V) with a halide to form a β-halide compound of the following formula: wherein R 1 , R 2a , R 3a , R 4 , R 5 and R′ are each as defined above, and X represents halo; (4) deprotecting a hydroxy protective group of the compound of formula (VI) to form a compound of the following formula: wherein R 1 , R 2 , R 3 , R 4 , R 5 , and X are each as defined above; (5) performing intramolecular cyclization to the compound of formula (VII) to form the compound of formula (I).