Tandem Beckmann and Huisgen–White rearrangement as an alternative to the Baeyer–Villiger oxidation of the bicyclo[3.3.1]nonane system: first asymmetric synthesis of (–)-dihydropalustramic acid. X-Ray molecular structure of 2β-ethyl-9-phenylsulfonyl-9-azabicyclo[3.3.1]nonan-3-one

Abstract

The transformation of the ‘fork head ketone’ 3b into the corresponding bicyclic lactone 13 via the Beckmann followed by the Huisgen–White rearrangement is described. Application of the method to a homochiral 2-etyl-substituted bicyclic ketone (+)-3dα gave efficiently (–)-dihydropalustramic acid (–)-2a, a degradation product from the alkaloid palustrine 1, in good optical yield.