An intermediate for the synthesis of the a - ring part of vitamin d derivatives with a substituent in the 2 - position

摘要

Novel compounds corresponding to the A ring moiety of 2-substituted vitamin D derivatives, namely, compounds represented by general formula (1), intermediate compounds for synthesizing the above compounds and a process for producing the above compounds, wherein R?1, R2 and R3¿ are the same or different and each represents hydrogen or a protective group; and R4 represents lower alkyl.