New chiral building blocks from tetrabromocyclopropene and furan.

The cyclocondensation of tetrabromocyclopropene and furan leads directly to a halogenated oxabicyclo[3.2.1]octadiene derivative. Over the past several years, we have utilized these compounds as intermediates for natural product synthesis. Herein, we describe the preparation of nonracemic dibromoenone building blocks from the racemic cycloadduct. Conversion of the adduct to a mixture of tartrate-derived ketals followed by separation of the diastereomers and hydrolysis allows for the formation of novel chiral synthons with either absolute configuration. Copyright 2004 American Chemical Society