DIRECT PREPARATION OF (Z,Z)-1,4-DIENIC UNITS WITH A NEW C6 HOMOLOGATING AGENT - SYNTHESIS OF ALPHA-LINOLENIC ACID

Syntheses of two C6 homologating agents 2a and 2f are described. These agents allow direct access to the (Z,Z)-1,4-diene unit 3, a moiety pr esent in a wide number of natural compounds. Compound 2a is prepared i n 40% overall yield by selective epoxidation of methoxycyclohexa-1,4-d iene followed by oxidative ring cleavage and transacetalization. Compo und 2f is obtained in 90% yield by a one-step oxidative dimerization o f phosphonium salt 1. A short synthetic application of these two new C 6 homologating agents to the synthesis of alpha-linolenic acid is desc ribed.