Precursors of the A-ring of vitamin D and method and intermediates for the preparation thereof

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 asymmetrization of 3,5-dihydroxybenzoic acid derivatives, as well as intermediates of preparation of said compounds.