Precursors of D vitamin, process of their preparation and intermediates of such preparation process

摘要

The invention relates to precursors of the A-ring of vitamin D, of the formula (I) : in which A, R, R1 and R2 are as defined in the specification. The invention also relates to a method of preparing compounds (I) comprising the enzymatic asymmetrisation of 3,5-dihydroxybenzoic acid derivatives, as well as intermediates of preparation of said compounds.