Synthesis of the bisbenzannelated spiroketal core of the γ‐rubromycins. The use of a novel Nef‐type reaction mediated by Pearlman’s catalyst

The synthesis of the bisbenzannelated spiroketal core 6 of γ-rubromycin 1 from the substituted nitrostyrene 20 was achieved by using a novel Nef-type reaction mediated by Pearlman’s catalyst. The precursor 28 was synthesised from readily prepared starting materials using Henry condensation chemistry. The product 6 was found to exist in two conformations in solution as shown by NMR spectroscopy.