Isolation of 4-Hydroxy-5-methyl-3(2H)-furanone,a Flavor Component in Shoyu (Soy Sauce)

An analytical method was developed for determining the four optical isomers of a new synthetic pyrethroidal insecticide, α-cyano-3-phenoxy-benzyl 2-(4-chlorophenyl)isovalerate (Fenvalerate, S–5602). The cyano group in S–5602 molecule was converted into l-menthyloxycarbonyl group by heating S–5602 with l-menthol and hydrochloric acid. The obtained diastereoisomer derivative (l-menthyl ester deriv.) was chromatographed on a μPorasil column (4 mm i.d. × 0.3 m) using a solvent system of hexane-ethyl acetate (500+7, v/v) as a mobile phase, and the four isomers of S–5602 were separated from one another within 20 min. The compositions of S–5602 isomers were determined from their peak areas.