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

Abstract

AbstractThe 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)