PROCESS FOR PRODUCING VITAMIN A OR ITS CARBOXYLIC ACID ESTERS, AND INTERMEDIATE COMPOUNDS USEFUL FOR THE PROCESS

摘要

A process for producing vitamin A represented by the formula (I) which comprises treating a compound represented by the formula (IIa-2) (IIb) (IIc) wherein R1 represents an aryl group which may be substituted, R21 and R22 each represents a hydrogen atom or a lower alkanoyl group, R3 represents an acetal-type protective group for a hydroxyl group, and X represents a halogen atom, with a base; and novel intermediate compounds useful for the above process.