In order to carry out one-pot syntheses of the sex pheromone homologs of a codling moth, Laspeyresia promonella L. by use of a thermophilic enzyme, we have examined the reactivities of 3-methylhex-2-enyl diphosphates as an allylic substrate and of some 3-alkyl homologs of isopentenyl diphosphate in the reaction catalyzed by farnesyl diphosphate (FPP) synthase of Bacillus stearothermophilus.3-methylhex-2-enyl diphosphate (1a) was accepted as a substrate with 3-ethylbut-3-enyl diphosphate (2b) to give a mixture of (2E,6E)-3-ethyl-7-methyldeca-2,6-dienyl- (3b) and (2E, 6E, 10E)-3,7-diethyl-11-methyltetradeca-2,6,10-trienyl diphosphate (4b). 1a was also reacted with 3-propylbut-3-enyl diphosphate (2c) to give exclusively (2E,6E)-7-methyl-3 propyldeca-2,6-dienyl diphosphate (3c). On the other hand, Z-3-methylhex-2-enyl diphosphate (1b) was accepted as a substrate with 2b to give a mixture of (2E,6Z)-3-ethyl-7-methyldeca-2,6-dienyl- (3'b) and (2E,6E,10Z)-3,7-diethyl-11-methyltetradeca-2,6,10-trienyl diphosphate (4'b). The Z-isomer (1b) was reacted with 2c to give (2E,6Z)-7-methyl-3 propyldeca-2,6-dienyl diphosphate (3'c).On the basis of these reactivities, one-pot enzymatic syntheses of the sex pheromone homologs of the codling moth, 3c-OH and 3'c-OH, were carried out by the action of the FPP synthase, followed by an alkaline phosphatase, with yields of 9.6% and 0.6%, respectively.