Abstract: This paper reports a ten-step stereoselective synthesis of the racemic a, P- unsaturated lactone 3, which has been obtained previously in optically active form by degradation of triacetylandrographolide. The stereochemistry of ring fusion and the relative configurations of the substituents at C-4 in the crucial bicyclic intermediate 22 were established by chemical reactions and analysis of the nmr spectra of compounds 18b and ...
