The Alkaloids of Crotalaria goreensis Guill. et Perr.: 7β-Hydroxy-1-methylene-8β- and 7β-Hydroxy-1-methylene-8α-pyrrolizidine

Abstract

The principal alkaloid of Crotalaria goreensis Guill. et Perr. is 7β-hydroxy-1-methylene-8β-pyrrolizidine (II),* a (+)-heliotridane derivative with the relative configuration of heliotridine at C7 (absolute configuration 7R, 88). Of two minor alkaloids isolated, one is the 7β-hydroxy-8α diastereoisomer (V) (absolute configuration 7R, 8R). The other minor alkaloid is isomeric with (II) and (V) but does not possess a 1-methylene group. The alkaloid (V) and the enantiomer of the principal alkaloid have been synthesized by reduction of the appropriate 1-chloromethyl-7-hydroxy-1,2-dehydropyrrolizidine with zinc and sulphuric acid. In this reduction some of the 1-methyl-1,2-dehydropyrrolizidine is formed but the 1-methylenepyrrolizidine is the main product.