Biogenetic-Type Transformation of Germacranolide to Melampolides

Department of Chemistry, Indian Institiite of Technology, Powai, Bombay-400 076 Department of Chemistry, Florida State University, Tallahassee, Florida 32306 (USA) A direct, single-step, biogenetic-type oxidative transformation of costunolide (I), the structural prototype of the germacranolides with ∆4 (5) trans- ∆1(10) trans-double bonds, using selenium dioxide, led to the formation of two melampolides, (XIII) and (XIV), with ∆4 (5) trans- ∆1(10) cis configurations. In addition to the chemical evidence, spectral data including NOE, are adduced to establish the stereostructures of the products