The Total Synthesis of (-)-7-Deoxyloganin via N-Heterocyclic Carbene Catalyzed Rearrangement of α,β-Unsaturated Enol Esters

The diastereoselective N-heterocyclic carbene (NHC) catalyzed rearrangement of alpha,beta-unsaturated enol ester (S)-2b has been used to assemble dihydropyranone (S)-3b, a material embodying the bicyclic core of the iridoid family of natural products. Elaboration of this intermediate, by chemoselective reduction followed by stereoselective beta-glycosylation, has allowed the total synthesis of (-)-7-deoxyloganin (1) to be achieved in four subsequent steps.