Abstract: Formula (I) in which: R1 and R2, which may be the same or different, each represents a lower alkyl, alkenyl or alkynyl group; R3 represents a methyl group having ?- or ?-configuration; R4 represents a hydrogen atom or an etherifying or esterifying group; R5 represents a hydrogen atom, a hydroxyl group or a lower alkoxy group; X represents a group OR4, or a group NR6R7 wherein R6 represents a hydrogen atom, an aliphatic or araliphatic group, or an acyl group comprising an aliphatic, araliphatic or aryl group linked to the nitrogen atom by way of a carbonyl group; and R7 is a hydrogen atom or a lower alkyl group; Y represents a lower alkylene, alkenylene or alkynylene group optionally substituted by a hydroxyl, etherified hydroxyl or esterified hydroxyl group; exhibit potent effects on modulation of cell growth and differentiation, while having low calcaemic activity.

Abstract: Compounds of Formula (I) in which: R1 and R2, which may be the same or different, each represents a lower alkyl, alkenyl or alkynyl group; R3 represents a methyl group having ?- or ?-configuration; R4 represents a hydrogen atom or an etherifying or esterifying group; R5 represents a hydrogen atom, a hydroxyl group or a lower alkoxy group; X represents a group OR4, wherein R4 is as defined above, or a group NR6R7 wherein R6 represents a hydrogen atom, an aliphatic or araliphatic organic group, or an acyl group comprising an aliphatic, araliphatic or aryl organic group linked to the nitrogen atom by way of a carbonyl group; and R7 is a hydrogen atom or a lower alkyl group; Y represents a lower alkylene, alkenylene or alkynylene group optionally substituted by a hydroxyl, etherified hydroxyl or esterified hydroxyl group; and the dotted lines signify that double bonds may be present at the 16(17)-position and/or either at the 6(7)- and 8(9)-positions or at the 7(8)-position exhibit potent effects on modulation of