Stereoselective Syntheses of Cis- and Trans-Isomers of alpha-Hydroxy-alpha,beta-dibenzyl-gamma-butyrolactone Lignans: New Syntheses of (+/-)-Trachelogenin and (+/-)-Guayadequiol.

Cis- and trans-isomers of α-hydroxy-α,β-dibenzyl-γ-butyrolactone lignans 1a,d−g and 2a,c,d were stereoselectively synthesized in good yields based on the electrophilic addition to the metal enolate of α-benzyl-γ-butyrolactone derivatives 1l−o and 3 as a key step. This method was applied to the syntheses of (±)-trachelogenin and (±)-guayadequiol, representative examples of the trans- and cis-isomers of α-hydroxy-α,β-dibenzyl-γ-butyrolactone lignan series.