butoxycarbonyl-2-methylpropanoic acid (D) and (2R,6S)-7acetoxy-2,6-dimethyl-1-heptanol (G), by employing lipase-dodecyl propanoate (1 and 2), the components of the pheromone of Microdiprion pallipes, were synthesized from catalyzed kinetic resolution in a later step. two chiral and nonracemic building blocks, (R)-3-tert-Pine sawflies, which are classified into more than 120 species, are serious pests on pines in the northern part of the world. [1] The minor pine sawfly, Microdiprion pallipes, occurs in Northern Europe and Asia. In 1998 its femaleproduced sex pheromone was identified as 1,2,6,10-tetramethyldodecyl propanoate by BergstrΓΆm et al. [2] Synthesis and field experiments of its stereoisomers by Larsson et al. revealed that (1S,2S,6S,10R)-1 and (1S,2R,6R,10R)-2 catch male M. pallipes. [3] There are numerous reports on the synthesis of pine sawfly pheromones including our own enantioselective synthesis in 1979. The recorded syntheses of pine sawfly pheromones were previously reviewed twice. [5] [6] Even after 1990, the activity in this area of synthesis still continues, reflecting the ecological importance of clarifying the chemical communication system of the pine sawflies. [1,7Οͺ10] We report herein the synthesis of 1 and 2 based on the use of enzymatic systems in enantioselective transformations. [11] Scheme 1 shows the retrosynthetic analysis of (1S,2S,6S,10R)-1. The target molecule 1 can be dissected between C-7 and C-8 to give the building blocks A and B. The bromide A can be prepared from the known compound C, which can be derived from D. The half ester D is an industrial building block manufactured biochemically by Mitsubishi Rayon Co. [13] Another building block B is obtainable from E and F, the former of which can be derived from the known monoacetate G. [14] Synthesis of 2 is also possible by starting from the same building blocks D, G Scheme 1. Structures of the components 1 and 2 of the sex phero- mone of Microdiprion pallipes and the retrosynthetic analysis of 1 and F.
Preparation of the building block A (Ο 9) was executed in a conventional manner as summarized in Scheme 2. displaced by a cyanide anion to furnish the nitrile 5. Acid hydrolysis of 5 gave the acid 6, which was reduced with Treatment of (R)-2-methyl-1-butanol (3) with tosyl chloride in pyridine yielded the tosylate 4, whose tosyloxy group was lithium aluminum hydride to afford the alcohol 7. The alcohol was then converted into the corresponding bromide [ ] Part CXCVII: Ref. 9 via the tosylate 8. The overall yield of 9 was 60% based [a] Department of Chemistry, Faculty of Science, on 3 (6 steps).