| abstract |
A process for preparing vitamin D derivatives having the following formula:wherein R1, R2, R3, and R4, which may be the same or different, represent a hydrogen atom or a protecting group, comprising:reacting a compound of formula (2) wherein R1 represents a hydrogen atom or a protecting group, with a compound having the formula (3) wherein R1 represents a hydrogen atom and R2, R3, and R4, which are the same or different, represent a hydrogen atom or a protecting group. |