Synthesis of the 5,6-dihydro-2-pyrone moiety of (+)-anamarin

Abstract

The α,β-unsaturated δ-lactone (+)-goniothalamin (18E) and its Z-isomer (18Z), which contain the lactonic moiety of (+)-anamarin (1), have been synthesized from the known 1,2-O-isopropylidene-3-deoxy-α-D-glucofuranose (7). In the key step, methyl 3,5-dideoxy-β-D-glucofuranuronate (15) was treated with benzylidenetriphenylphosphorane in dimethyl sulphoxide to give the E- and Z-β-hydroxy δlactones (17). These were then transformed into the 5,6-dihydro-2-pyrones (18), and also into the aldehyde (20), intended for use in a total synthesis of (+)-anamarin (1).