Stereoselective reactions. V. Design of the asymmetric synthesis of lignan lactones. Synthesis of optically active podorhizon and deoxypodorhizon by 1,3-asymmetric induction.

A novel method for the asymmetric synthesis of both enantiomers of 2, 3-disubstituted-butanolides (8) was devised using a readily available (S)-4-hydroxymethyl-4-butanolide 4-derivative (6) as a chiral source in the asymmetric induction and as the carbon framework of 8. Application of this method to the asymmetric total synthesis of podorhizon (23) and deoxypodorhizon (4) is described.