Peptides with para-substituted phenylalanine

摘要

Somatostatin peptides are modified by substitution of para-methoxylated Phe or para-halogenated Phe for any Phe in the peptide. The modified somatostatin peptide analogs have the formulae: I II wherein R is hydrogen or an acyl group; R1 is selected from the group consisting of Lys or Des R1; R2 is selected from the group consisting of Asn, Ala or Des R2. The amino acids of the R2 group can be either the L-form or the D-form; R3 is selected from the group consisting of Trp or D-Trp; R4 is selected from the group consisting of Thr or Des R4; R5 is selected from the group consisting of Ser, D-Ser, Phe, X or Des R5; and X is selected from the group consisting of Phe, para-halogenated Phe and para-methoxylated Phe. Provided that at least one X is either para-halogenated Phe or para-methoxylated Phe.