Synthesis of (4 E ,7 S )‐(−)‐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, Heptyloxirane ( 3 ) and the alkyne 4 containing the carboxyl group masked as a tricyclic orthoester were prepared by known methods from 5 and 6 as starting materials. Reaction of lithiated 4 with 3 afforded in 74% yield the alkyne 2 which could easily be transformed into the target molecule. Hydrogenation with Lindlar catalyst produced 7 which could be isomerized to 8 with ( E ) configuration. Methylation of the 7‐hydroxy group in 8 gave 9 which could be transformed into the methyl ester 10 and the (4 E,7S )‐acid 1 in high yield.