Improved scalable syntheses of mono- and bis-urethane derivatives of ornithine

Abstract

In the search for a practical route to ornithine bisurethane derivatives useful for peptide synthesis, we elaborated the simple and efficient (86% yield) synthesis of Nε-tert-butoxycarbonyl-L-ornithine copper(II) complex(1). This served as substrate for obtaining Nε-tert-butoxycarbonyl-L-ornithine (2), Nα-benzyloxycarbonyl-Nε-tert- butoxycarbonyl-L-ornithine (3) and Nα-(9-fluorenyl)methoxycarbonyl-Nε-tert- butoxycarbonyl-L-ornithine (4). These were synthesized in 94-95% yields and with a purity above 99%.