The Gracilines: A Novel Subgroup of the Amaryllidaceae Alkaloids

Abstract

A new subgroup of the Amaryllidaceae alkaloids having a lob,&-ethanoiminodibenzo[b,dlpyrane (2-henzopyrano[3,~indole) nucleus is isolated from two different Galanthus species as three novel monomeric alkaloids, (+)-graciline ( I ) , (+)-11-acetoxygraciline ( 2 ) and (+)-3.4-dihydro-3-hydroxygraciline(3).The fourth new compound, (-)-digracine (4) is a dimer of two such moieties.The Amaryllidaceae alkaloids constitute an exclusive group of basic compounds elaborated almost solely by species of the specified plant family.These alkaloids, some of which display remarkable physiological and pharmacological activitie~,"~ have so far been classified on structural considerations into eight s u b g r o u p s .' A thorough literature survey has revealed that the members of the