abstract |
The invention relates to a process for the preparation of vitamin D3 compounds of formula I. wherein A is a single or a double bond; B is a single, cis-double, trans double or a triple bond; R1 and R2 are independently hydrogen, a C1-C4 alkyl; R3 and R4 are independently a C1-C4 alkyl, a hydroxyalkyl, and a haloalkyl; and X and Y are independently hydrogen or hydroxy in the case when B is a single or a double bond. |