First Asymmetric Synthesis of (+)-Sordidin and (–)-7-epi-Sordidin, Aggregation Pheromones of the Banana Weevil Cosmopolites sordidus



The asymmetric synthesis of (1S,3R,5R,7S)-(+)-sordidin and 7-epi-(1S,3R,5R,7R)-(–)-sordidin, both components of the natural male-produced aggregation pheromone of the banana weevil Cosmopolites sordidus (Germar), starting from 2,2-dimethyl-1,3-dioxan-5-one is described. Two of the stereogenic centers were generated by three α-alkylations of the corresponding RAMP-hydrazone. Diastereoselective epoxide opening as another key step of the synthesis employing the aza-enolate of 3-pentanone SAEP-hydrazone as nucleophile and subsequent acidic intramolecular acetalisation furnished the sordidin C-7 epimers in good overall yield (39 %) as a 1.5:1 diastereomeric mixture. The epimers could be separated by preparative GC and thus, each of them could be obtained in high diastereomeric and enantiomeric purity (de ≥ 97 %, ee ≥ 98 %). (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)