Reactivity and conformational study of germacranolides

Abstract

Germacranes are an important group of sesquiterpenes widely occurring in nature and considered as key intermediates in the biosynthesis of other sesquiterpenes. They share a cyclodecadiene ring characterized by their ability to undergo conformational changes, their great tendency to undergo Cope rearrangement and transformation to a large variety of products upon acid or irradiation treatment. One of the most important class of secondary metabolites, showing the germacrane skeleton are the germacranolides, considered as biogenetic precursors for other related skeletal types of lactones. A signicant number of these ones has demonstrated a broad spectrum of biological activities. Recently information has been collected on their antitumor activity. The wide range of reactions experienced by germacranolides makes this group of compounds as key intermediates for the synthesis of a great variety of compounds. Moreover, the ring systems of these compounds possess a conformational flexibility so that exists as a mixture of conformers, very close in energy and interchangeable though very small energy barriers, which makes then very interesting. In this work, a review concerning the reactivity of these compounds was carried out through various types of reaction: Cope, Electrophilic Cyclizations and UV irradiation.