Isothiourea-catalyzed enantioselective functionalisation of glycine Schiff base aryl esters via 1,6- and 1,4-additions

Abstract

The enantioselective α-functionalisation of glycine Schiff base aryl esters through isothiourea catalysis is successfully demonstrated for 1,6-additions to para-quinone methides (21 examples, up to 95 : 5 dr and 96 : 4 er) and 1,4- additions to methylene substituted dicarbonyl or disulfonyl Michael acceptors (17 examples, up to 98 : 2 er). This nucleophilic organocatalysis approach gives access to a range of α-functionalised α-amino acid derivatives and further transformations of the activated aryl ester group provide a straightforward entry to advanced amino acid-based esters, amides or thioesters.