title: Stereoselective Syntheses of (-)-Podorhizol Lignan and its Derivatives: erythro and threo Preferential Aldol Condensation of Potassium Enolate from γ-Butyrolactone with Alkoxybenzaldehyde.
abstract: (-)-Podorhizol (1) was stereoselectively synthesized by erythro preferential aldol condensation of 3,4,5-trimethoxy- benzaldehyde with potassium enolate from (+)-(R)-3- (3,4-methylenedioxybenzyl)-4-butanolide (2) (erythro:threo=85:15). Erythro selectivity was observed in the aldol condensation of many alkoxybenzaldehydes with potassium enolate from (+)-γ-butyrolactone 2. However, benzaldehydes having methoxy groups at both the 2 and 6 positions gave threo selectivity in the aldol condensation with potassium enolate from (+)-γ-butyrolactone 2.
authors.affiliation: a College of Agriculture, Ehime University.
authors.forename: S
authors.initials: S
authors.lastname: Yamauchi
authors.affiliation: a College of Agriculture, Ehime University.
authors.forename: M
authors.initials: M
authors.lastname: Machi
authors.affiliation: a College of Agriculture, Ehime University.
authors.forename: Y
authors.initials: Y
authors.lastname: Kinoshita
keywords: aldol condensation; dibenzyl-γ-butyrolactone; lignan; podorhizol; γ-butyrolactone