Total Synthesis of Dumsin. 1. Retrosynthetic Strategy and the Elaboration of Key Intermediates from (−)-Bornyl Acetate

Abstract

An intramolecular anionic oxy-Cope rearrangement (44 --> 46) serves as the key step in a synthetic approach to the insect antifeedant dumsin. Initial investigations clarified the manner in which (--)-bornyl acetate may be transformed into the exo-norbornenol 44. Two routes were developed to advance beyond 46. The first involved acetal 51 as a matrix that was expected to allow the elaboration of rings D and E. The second plan deferred oxidation of the cyclopentene ring in 46 to a later stage of molecular construction. The latter experiments formed the basis of a protocol that led to the successful acquisition of keto aldehydes typified by 108 and 114.