Concise formal synthesis of (−)-7-deoxyloganinvia N-heterocyclic carbene catalysed rearrangement of α,β-unsaturated enol esters

Abstract

NHC catalysed rearrangement of α,β-unsaturated enol esters derived from formyl acetates and cyclopentyl annulated α,β-unsaturated acids provides the cyclopentapyranone core of (−)-7-deoxyloganin (1) with diastereo- and chemoselectivity in 6 steps starting from (−)-citronellal. The elaboration to the natural product has been investigated using two new approaches. The most successful intercepts our previous work on (−)-7-deoxyloganin (1) allowing completion of a formal total synthesis in 10-steps.