Building addressable libraries: site-selective formation of an N-acyliminium ion intermediate.

A strategy for site-selectively generating reactive N-acyliminium ion intermediates on a microelectrode array has been developed. The route capitalizes on the use of an electroauxiliary for building a methoxylated amino acid substrate, and then the electrochemical generation and solution phase confinement of acid in order to form the N-acyliminium ion. Keys to this strategy were the stability of an N-alpha-methoxyalkyl amide to basic reaction conditions and the generality of the electrogenerated acid conditions for conducting microelectrode array reactions in a site-selective fashion.