Synthesis of β-amino-acid peptides. Part 2. Preparation of peptides of 3-amino-2,2-dimethylpropionic acid by means of conventional coupling reagents and with oxazin-6-one derivatives

Abstract

Side reactions were encountered during the coupling of 3-amino-2,2-dimethylpropionic acid (β-Api) derivatives, some of which could be directly ascribed to steric hindrance at the carboxy-group. Protected and deprotected tri- and hexa-peptides were prepared using dicyclohexylcarbodi-imide and hydroxybenzotriazole. Alternative procedures employing oxazin-6-ones were not as useful as expected.