A Concise Approach to Oxo-Dehydrorotenoid by Direct Lactonization and the Total Syntheses of Stemonone, Rotenonone, 6-Oxo-dehydroelliptone, and 6-Oxo-6a,12a-dehydrodeguelin
An approach to construct the oxo‐dehydrorotenoids via direct lactonization of isoflavone‐2‐carboxylic acids is reported. The application of this method for the first total syntheses of the natural products, stemonone, 6‐oxo‐dehydroelliptone, rotenonone, and 6‐oxo‐6a,12a‐dehydrodeguelin, are demonstrated. The series of oxo‐dehydrorotenoids was also evaluated for their biological activities.
The regioselective cyclization/dehydration sequence of ortho diketo phenoxyethers induced by DBU has been explored. The results demonstrated a high degree of selectivity with preference for 6-exo-trig cyclization leading to the formation of gamma-benzopyranone derivatives in good yield. (C) 2013 Elsevier Ltd. All rights reserved.