Synthesis and stereochemical behaviour of 8-alkyl-3-(1-phenylethyl)-7-oxa-1,3-diazabicyclo-[3.2.1]-octane-4,6-diones directed towards the synthesis of α-substituted β-amino acids

Abstract

A diastereoselective synthesis of enantiomerically pure α-hydroxymethyl β-amino acid derivatives is described starting from α,β-unsaturated acids. The unsaturated acids are transformed through simple steps into chiral perhydropyrimidin-4-ones that are diastereoselectively transformed into [3.2.1]-1,3-diaza-7-oxabicyclooctan-4,6-diones by reaction with LiHMDS. The bicycle 9b is opened by reaction with methanol under acid catalysis and the product 10 is selectively reduced to afford the desired compound.