The building block approach to unusual alpha-amino acid derivatives and peptides.

The building block approach was identified as a useful alternative to the commonly used Bücherer-Berg method for the preparation of cyclic unusual alpha-amino acid derivatives. The symmetrical building blocks were prepared by dialkylation of ethyl isocyanoacetate under solid-liquid phase transfer catalysis conditions while the unsymmetrical building blocks were prepared by a stepwise alkylation of the O'Donnell Schiff base. Metathesis reactions, Suzuki couplings, and cycloaddition reactions were utilized to assemble the building blocks.