Palladium-catalyzed cyclization reactions of acetylene-containing amino acids

Enantiomerically pure acetylene-containing alpha-amino acids were used as versatile starting materials for the synthesis of a variety of heterocycles via Pd-mediated cyclization reactions. Depending on the protecting group strategy, both the carboxylate and the amine function of the amino acids could participate in the cyclizations, thus giving rise to oxygen heterocycles (alpha-aminolactones) and nitrogen heterocycles (cyclic alpha-amino acid derivatives), respectively. Beside the straight forward cyclization, cyclization/cross-coupling reactions were also successfully carried out to provide the corresponding substituted cyclic amino acid derivatives.