Intramolecularacylation of an organolithium leads to an efficient stereocontrolled total synthesis of both enantiomers of sundiversifolide. The absolute configuration was determined by HPLC analysis and allelopathy assay. The gamma-lactone moiety resulted from a butenolide was obtained by the condensation of a bicyclic alpha-hydroxyhemiacetal with Ph3P=CMe(CO2R).
The total synthesis and determination of the absolute configuration of (+)- and (-)-sundiversifolide have been achieved via intramolecular acylation and Wittig-lactonization as the key steps. The xanthanolide sesquiterpene lactones, 8-epi-xanthatin (1), dihydroxanthatin (2), and xanthatin (3) were also prepared, starting from a common intermediate derived from the synthesis of sundiversifolide. (C) 2010 Elsevier Ltd. All rights reserved.