Decarboxylative Radical Addition to Methylideneoxazolidinones for Stereocontrolled Synthesis of Selectively Protected Diamino Diacids

Abstract

Syntheses of stereochemically pure and selectively protected diamino diacids can be achieved by redox decarboxylation of distal N-hydroxyphthalimide esters of protected aspartic, glutamic or α-aminoadipic acids via radical addition to methylideneoxazolidinones. The products are useful for solid-supported syntheses of robust bioactive carbocyclic peptide analogs. Yields of reactive primary radical addition are superior to those of more stabilized radicals, and the reaction fails if the alkylideneoxazolidinone has a methyl substituent on its terminus (i.e., 13a/13b).