PURPOSE: To obtain a vitamin d3 derivative containing a carbonyl group at a part corresponding to 24-position of 22-oxavitamin D3 useful as a medicine, having strongly differentiation-inducing action.

CONSTITUTION: This compound is shown by formula I [R1 is H or OH; A is a substitutable 1-4C alkylene; B is a group of formula II (R2 and R3 are each a 1-4C alkyl; R4 is H or OH) or a substitutable cyclic hydrocarbon or heterocycle] such as 1α, 3β-dihydroxy-20(S)-(3-hydroxy-3-methyl-2- oxobutyloxy)-9,10-secopregna-5,7,10(19)-triene. The compound of formula I is obtained by reacting 20(S)-hydroxy-1α, 3β-bis(t-butyldimethylsilyloxy)pregna-5,7- diene of formula III with a compound of the formula R5X (R5 is a group of formula IV; A is a 1-4C alkylene; X is an eliminable group such a halogen or methanesulfonyloxy) in the presence of a base.