Pheromones of Vespa orientalis

R,6R) diastereoisomer (Scheme 7). Again, from 34 the (5R,6R) product 43 was obtained. Products 42 and 43 represent the two enantiomers of the proposed major component of a mosquito oviposi-tion attractant pheromone (18). The enantiomeric forms of 5-hexadecanolide, 44 and 45, the pheromone of Vespa orientalis, were obtained from the enantiomeric aldehydes 34 and 37 (19). All the compounds obtained up to this point have been prepared in both enantiomeric forms, starting from a single chiral material. 

Kinetic resolution of chiral acetals has been effected by use of some organoaluminum reagents [84], On treating a chiral acetal 88, derived from (2, 4/ )-(-)-pentanediol, with -Bu3A1 at room temperature, one diastereomer was found to react much faster than the other, and the residu enol ether is transformed into optically pure ketone. The efficiency of this method is demonstrated by a concise synthesis of (5)-(-)-5-hexadecan-l,5-lactone (89), the pheromone of Vespa orientalis, as shown in Sch. 56. 

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