Sequential polypeptides. Part V. The use of monoesters of catechol in the synthesis of sequential polypeptides with amino- or carboxy-side-chains

Abstract

Benzyloxycarbonylpeptide 2-benzyloxyphenyl esters with side-chain protection based on t-butyl alcohol can be deprotected without difficulty by hydrogenolysis in acetic acid, provided sulphur-containing reagents are avoided at all previous stages. The resulting peptide 2-hydroxyphenyl ester acetate salts are not isolated but are immediately polymerised by means of triethylamine in dimethyl sulphoxide. Hydrogenolysis of N(α)-benzyloxycarbonyl-N(ε)-t-butoxycarbonyl-L-lysyl-L-alanyl-L-alanine 2-benzyloxyphenyl ester and polymerisation of the active ester derivative thus obtained gave a protected polymer from which poly(L-lysyl-L-alanyl-L-alanine) was obtained after trifluoroacetic acid treatment, dialysis, and lyophilisation. Poly(L-glutamyl-L-alanyl-L-alanine) was similarly prepared.