A new pyrrolizidine alkaloid, broussonetine N, as an inhibitor of glycosidase, from Broussonetia kazinoki SIEB. and absolute stereostructures of broussonetines A and B

Abstract

A new pyrrolizidine alkaloid, broussonetine N, was isolated from the branches of Broussonetia kazinoki SIEB. (Moraceae). Broussonetine N was formulated as (1R,2R,3R,5S,8R)-1,2-dihydroxy-3-hydroxymethyl-5-[(1R)-1,10- dihydroxy-6-oxo-decyl] pyrrolizidine (1) by spectroscopic and chemical methods. 1 inhibited β-glucosidase, β-galactosidase, and β-mannosidase. Absolute stereostructures of broussonetines A (2) and B (3) as well as that of 1 were also determined by a new version of Mosher's method.