Patent ID: 6967195

Claim:
Compounds of formula (I) in which: R 1 represents a hydrogen atom or an O-protecting group; R 2 represents a hydroxyl, lower alkoxy, carboxaldehyde, lower alk-1-enyl or hydroxy- or lower alkoxy-substituted lower alkyl group; R 3 represents a methyl group having α- or β-configuration; X represents a C 1-3 alkylene group or a valence bond; Y represents a carboxaldehyde group or a group of formula —C(R 4 )(R 5 )OR 1 where R 1 is as defined above and R 4 and R 5 , which may be the same or different, are each selected from hydrogen atoms, alkyl, alkenyl and alkynyl groups such that the total carbon content of R 4 and R 5 does not exceed three atoms, with the proviso that X is a valence bond when both R 4 and R 5 are other than hydrogen; and the dotted line signifies that a double bond may optionally be present at the 16(17)-position.