intermediat for the synthesis of a ringteils of vitamin d derivatives with substituents in the 2 - position

摘要

The object of the present invention is to provide novel compounds corresponding to the A ring part of vitamin D derivatives having a substituent at the 2-position. According to the present invention, there are provided compounds of the general formula (1): CHEM (wherein R1, R2 and R3, which may be the same or different, represent a hydrogen atom or a protecting group and R4 represents a lower alkyl group), intermediates for synthesizing them and a process for preparing them.