Improved Syntheses of N^ε-Tert-butyloxycarbonyl-L-lysine and Nα-Benzyloxycarbonyl-N^ε-tert-butyloxycarbonyl-I-lysine

Abstract

N^ε-tert-butyloxycarbonyl-L-lysine [4, H-Lys(BOC)-OH] and Nα-benzyloxycarbonyl-N^ε-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 somatostatin^3–5 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 low^11,12 and, in our hands, often irreproducable yields. In addition, dangerous and/or obnoxious reagents (e.g., tert-butyl-