Lewis acid-promoted α-hydroxy β-dicarbonyl to α-ketol ester rearrangement

The decarbomethoxylation reaction of a substituted alpha-hydroxy-alpha-carbomethoxy pentacyclic substituted ketone, used as an advanced intermediate in the synthesis of the alkaloid aspidophytine, can be effected by heating with MgI2 in CH3CN. The reaction was shown to proceed by a novel a-hydroxy beta-dicarbonyl to alpha-ketol ester rearrangement. It was possible to isolate a carbonate intermediate in 75% yield, thereby providing support for the proposed pathway. (c) 2006 Elsevier Ltd. All rights reserved.