SYNTHESIS AND PROPERTIES OF HIGH-MOLECULAR-WEIGHT POLYPEPTIDES CONTAINING TRYPTOPHAN .2. COPOLYPEPTIDES OF TRYPTOPHAN WITH VARIOUS AMINO-ACIDS

High-purity N-carboxyl L-tryptophan anhydride (L-4-indoylmethyl-2,5-ox azolidinedione) was synthesized in good yield. Copolypeptides with a r andom sequence of L-trypophan (Trp) with glycine (Gly), L-alanine (Ala ), L-alpha-amino-n-butyric acid (Abu), L-n-valine (Nval), L-n-leucine (Nleu), L-leucine (Leu), L-gamma-methylglutamate (Glu(OMe)), and L-met hionine (Met) were synthesized by the copolymerization of the correspo nding N-carboxy-alpha-amino acid anhydrides (NCA) in solution. The rat e of polymerization of Trp NCA was less than that of the other amino a cid NCAs. The helix contents of the formed copolypeptides, estimated b y the circular dichroism (CD) spectra, were remarkably decreased at a content of about 8% of Trp involved in poly(Trp-co-Nval) (poly(Trp,Nva l)), poly(Trp-co-leu) (poly(Trp,Leu)), poly(Trp-co-Nleu) (poly(Trp,Nle u)), and poly(Trp-co-Glu(OMe)) (poly(Trp,Glu(OMe))), but was not decre ased at that percentage in poly(Trp-co-Met) (poly(Trp,Met)).