Elektrochemische Oxidation von ( S )‐Äpfelsäure‐Derivaten: ein Weg zu enantiomerenreinen alkylierten Malonaldehydsäure‐estern

Electrochemical Oxidation of ( S )‐Malic‐Acid Derivatives: a Route to Enantiomerically Pure Alkylmalonaldehydic Esters The 3,3‐dialkymalic‐acid diesters, prepared by the previously described diastereoselective alkylations through dilithium alkoxide enolates, are saponified to the monoesters containing a free α‐hydroxycarboxylic‐acid moiety( Scheme 3 ). The monoesters are subjected to electrochemical oxidative decarboxylation in MeOH . If the intermediate monoacids are purified, the malonaldehydic esters (2‐formy1‐2‐alkylcaroxylates) Obtained by this procedure are enantiomerically pure; they have the same structural features, i.e. two enantiotopic functionalized branches on the (persubstituted) stereogenic center, as the well known 3‐hydroxy‐2‐methylpropanoic acid (‘ Roche acid’) which was employed frequently as a starting material for the preparation of either enantiomer of various target molecules.