Improved Syntheses of Nε-Tert-butyloxycarbonyl-L-lysine and Nα-Benzyloxycarbonyl-Nε-tert-butyloxycarbonyl-I-lysine

Abstract Nε-tert-butyloxycarbonyl-L-lysine [4, H-Lys(BOC)-OH] and Nα-benzyloxycarbonyl-Nε-tert-butyloxycarbonyl-L-lysine [7, Z-Lys-(BOC)-OH] are valuable intermediates for peptide syntheses. They have been employed in, among others, solid-phase and/or solution syntheses of nonadecapeptide1 and tetracosapeptide2 segments of ACTH, of somatostatin3–5 and of human β-endorphin.6 We recently had the need to prepare substantial quantities of compounds 4 and 7. The reported syntheses of these materials, due mainly to the groups of Zervas,7,8 Schwyzer9 and Wünsch,10 are plagued by low11,12 and, in our hands, often irreproducable yields. In addition, dangerous and/or obnoxious reagents (e.g., tert-butyl-