To synthesize retinal without passing through unstable retinol by using a sulfonic acid obtained by coupling a specific cyclic sulfonic acid derivative with a specific aryl halide derivative.
Retinal is obtained by treating a sulfonaldehyde derivative expressed by formula I (Ar is an aryl) with a base. The derivative of formula I is obtained by oxidizing a hydroxysulfonic acid derivative of formula II (R is H or an OH-protecting group) to obtain a sulfone derivative of formula III and successively removing the OR group of the sulfone derivative of formula III. The sulfone, a starting material, is obtained by reacting a 10C cyclic sulfone derivative of formula IV with a 10C aryl halide derivative of formula V (X is a halogen; R1 and R2 are each an OH-protecting group) in the presence of a base. Thus, retinal, a basic raw material of carotenoid important as a medicine, a feed additive, etc., is stably and easily obtained.
KONYA NAOTO
SEKO SHINZO
