Synthesis of the Optical Isomers of 3-Methyl-6-isopropenyl-9-decen-1-yl Acetate, a Component of the California Red Scale Pheromone

Article abstract of DOI:10.1021/jo01299a038

The synthesis of the optical isomers of 3-methyl-6-isopropenyl-9-decen-1-yl acetate (1), a component of the California red scale pheromone, and the determination of their biological activity were completed.Initially, (+/-)-citronellol was converted in four steps to a mixture of all four diastereomers of 1, the key step being the reaction of lithium di(3-butenyl)cuprate with 6,7-epoxycitronellyl acetate (4).This mixture strongly attracted male California red scale.To determine which of the four diastereomers of 1 were biologically active, (3R,6RS)- and (3S,6RS)-1 were then prepared from (R)-(+)-citronellol and (S)-(-)-citronellol, respectively.Since the 3S,6RS diastereomeric mixture was found to be a powerful attractant whereas the 3R,6RS diastereomeric mixture was devoid of attractancy, the 3S,6R and 3S,6S diastereomers of 1 were then prepared.The key to the synthesis of each of these two diastereomers of 1 was the high-performance LC separation of the diastereomeric MTP esters 12a and 12b.Lithium aluminium hydride reduction of 12a and 12b gave the corresponding diols 11a and 11b, which were intermediates in the synthesis of (3S,6R)- and (3S,6S)-1, respectively.The assignment of absolute configuration at C-6 in diols 11a and 11b (and therefore of the diastereomers of 1) was made on the basis of induced CD spectra of each diol and of the closely related diol of (10S)-JH III (13).The 3S,6R diastereomer of 1 was found to be more attractive to male California red scale than was the 3S,6S diastereomer.The naturally occuring pheromone component 1, upon examination by capillary GLC under conditions which gave separation of the 3S,6R and 3S,6S diastereomers, eluted with the synthetic 3S,6R diastereomer.