The unnatural amino acid Lys(NH2), easily incorporated into a peptidyl-PEGA resin by N-electrophilic amination of the epsilon-amino group, was cleanly transformed on the solid phase into 6-hydroxynorleucine by air oxidation in the presence of bicarbonate ions followed by reduction of the hydroperoxy intermediate with a water soluble phosphine. (C) 1999 Elsevier Science Ltd. All rights reserved.