Abstract

PENTES, Howard G.; MACIAS, Francisco A.  and  FISCHER, Nikolaus H.. Preparation of 11-Hydroxylated 11,13-Dihydrosesquiterpene Lactones. Rev. Soc. Quím. Méx [online]. 2003, vol.47, n.2, pp.132-138. ISSN 0583-7693.

Hydroxylations of the α-position of lactonic carbonyl groups of four different skeletal types (germacranolides, eudesmanolides, guaianolides, and elemanolides) of 11,13-dihydrosesquiterpene lactones were achieved by LDA-mediated generation of the corresponding lactone enolates and trapping with gaseous oxygen or with a chiral oxidizing agent, (camphorylsulfonyl)oxaziridine. The oxidations with oxygen were non-stereospecific and generated both, the 11 α- and 11β-hydroxylactones in combined yields ranging from 13-47 % along with norsesquiterpene ketones which are most likely formed by decomposition of the hydroperoxide anion intermediates. Hydroxylation of the germacranolide-type 11,13-dihydroparthenolide with either (+)- or (−)-(camphorylsulfonyl)oxaziridine gave exclusively the 11β-hydroxylactone (66-72 %) with no detection of the norsesquiterpene ketone.

Keywords : Sesquiterpene lactones; hydroxylation; LDA; enolates; oxidations; norsesquiterpene ketones; germacranolides; eudesmanolides; guaranolides; elemanolides.