A Novel Synthesis of Sex Pheromone from the Longicorn Beetle(Psacothea hilaris)

An asymmetric synthesis of (8Z,21R)-21-methylpentatriacont-8-ene, the sex pheromone of the yellow-spotted longicorn beetle Psacothea hilaris, has been achieved using Evan’s induction as the key step. Based on the asymmetric methylation product of chiral (R)-4-benzyl-1,3-oxazolidin-2-one, the carbon chain of the target molecule was assembled through a C5+C12+C11+C8 sequence. (2R)-4-(Benzyloxy)-2-methylbutan-1-ol, which can be obtained from γ-lactone following Evan’s protocol, was connected to a C12 alkyl group. The chiral methyl group remained the key moiety (97% ee). After another Wittig reaction and catalytic hydrogenation step, the designed key intermediate (13R)-13-methylheptacosan-1-ol was obtained. Finally, after oxidation and Wittig reaction, the synthesis of the target molecule was completed in 10 linear steps with an ultra-high overall yield of 36.2%.