Chirale Synthesebausteine aus Aminosäuren über einen elektrochemischen Schlüsselschritt: Herstellung von (R)-2-tert-Butyl-3-methoxycarbonyl-1,3-oxazolinen aus (S)-Serin und (S)-Threonin

Abstract

The cyclic N,O-acetals from the methyl-esters of α-amino-β-hydroxy-carboxylic acids (serine, threonine) and pivalaldehyde (methyl 2,3-oxazolidine-4-carboxylates 4) are transformed into the diastereoisomerically pure hetereocycles 5a (cis) and 5b (cis-trans). Electrolysis of the corresponding acids (6) replaces the COOH- by an OAc-group, and elimination of acetic acid gives the oxazolines 1 and 2. These heterocycles, with a stereogenic acetal centre, contain a highly reactive double bond, which reacts regio- and diastereoselectively and renders these compounds useful chiral building blocks.