STEREOSPECIFIC SYNTHESIS OF SUSPENSOLIDE, A MALE-PRODUCED PHEROMONE OF THE CARIBBEAN FRUIT-FLY, ANASTREPHA-SUSPENSA (LOEW), AND THE MEXICAN FRUIT-FLY, ANASTREPHA LUDENS (LOEW)

An efficient synthesis of (E,E)-4,8-dimethyl-3,8-decadien-10-olide, suspensolide, a major component of the pheromone blend of the Caribbean and Mexican fruit flies, is described. The synthesis involves dicarboalumination of 1,6-heptadiyne with in situ conversion to a dialanate and reaction with paraformaldehyde. Monoprotection of the symmetrical diol formed in this process as the mono-THP derivative allowed conversion of the free hydroxyl to the chloride (NCS/DMS). Addition of one carbon to the chain was achieved by displacement of the chloride by cyanide (phase-transfer conditions) or the lithium salt of a thioorthoester. Hydrolysis of the masked carbonyls and deprotection of the omega-hydroxyl gave (E,E)-4,8-dimethyl-10-hydroxy-3,8-decadienoic acid. This diunsaturated hydroxy acid was cyclized to suspensolide in 30% yield using Mitsunobu conditions. The overall yield of suspensolide in this eight-step synthesis was 10%.