Epoxy lactones by photooxidative rearrangement of 6β-acetoxyvouacapane

The first study of photooxidation reaction of 6 beta-acetoxyvouacapane isolated from Caesalpinia platyloba is reported. The reaction yielded four new epoxy lactones, 6 beta-acetoxy-15,16 alpha-epoxy-13-spirocassa-12,16-olide, 6 beta-acetoxy-15,16 beta-epoxy-13-spirocassa-12,16-olide, 6 beta-acetoxy-12,13 beta-epoxycassa-16,12-olide and 6 beta-acetoxy-12,13 alpha-epoxycassa-16,12-olide. All the structures were supported by ID and 2D NMR spectroscopy as well as mass spectrometry. The stereochemistry was established on the base of single crystal X-ray diffraction. (C) 2017 Elsevier Ltd. All rights reserved.