SYNTHESIS OF (4E,7S)-(-)-7-METHOXY-4-TETRADECENOIC ACID, A MAJOR CONSTITUENT OF THE MARINE CYANOPHYTE LYNGBYA-MAJUSCULA

The metabolite of the marine cyanophyte Lyngbya majuscula (4E,7S)-(-)- 7-methoxy-4-tetradecenoic acid (1) has been synthesized for the first time in optically active form in eight steps in 20% overall yield. Hep tyloxirane (3) and the alkyne 4 containing the carboxyl group masked a s a tricyclic orthoester were prepared by known methods from 5 and 6 a s starting materials. Reaction of lithiated 4 with 3 afforded in 74% y ield the alkyne 2 which could easily be transformed into the target mo lecule. Hydrogenation with Lindlar catalyst produce 7 which could be i somerized to 8 with (E) configuration. Methylation of the 7-hydroxy gr oup in 8 gave 9 which could be transformed into the methyl ester 10 an d the (4E,7S)-acid 1 in high yield.