The absolute stereochemical characterization of two new jatrophane diterpenes from Euphorbia esula

Abstract

The structures and absolute stereochemistry of two moderately toxic jatrophane diterpenes of potential taxonomic importance, esulone A [(E)-(–)-(1 R,3S,8R,9S,11R,12S,13R,14R)-1,13-diacetoxy-9,11-dibenzoyloxy-8,14-dihydroxy-3,6,6,14-tetramethyl-10-methylene-trans-bicyclo[10.3.0]pentadec-4-ene-2,7-dione] and esulone B [(E)-(–)-(1R,3S,8R,9S,11 R,12S,13R,14R)-1,8,13-triacetoxy-9,11 -dibenzoyloxy-14-hydroxy-10-methylene-3,6,6,14-tetramethyl-trans-bicyclo[10.3.0]pentadec-4-ene-2,7-dione], isolated from Euphorbia esula roots were determined utilizing n.m.r. spectroscopy, X-ray crystallography, and exciton chirality techniques. Stereochemical assignment corrections for previously reported lathyrane and jatrophane diterpenes are discussed.