title: Structure-activity relationship studies optimizing the antiproliferative activity of novel cyclic somatostatin analogues containing a restrained cyclic beta-amino acid.
abstract: The cyclic somatostatin analogue cyclo[Pro(1)-Phe(2)-D-Trp(3)-Lys(4)-Thr(5)-Phe(6)] (L-363,301) displays high biological activity in inhibiting the release of growth hormone, insulin, and glucagon. According to the sequence of L-363,301, we synthesized a number of cyclic hexa- and pentapeptides containing nonnatural alpha- and beta-amino acids. The N- fluorenylmethoxycarbonyl protected cyclic beta-amino acid [1S, 2S, 5R]-2-amino-3,5-dimethyl-2-cyclohex-3-enecarboxylic acid (cbetaAA), for the replacement of the Phe(6)-Pro(1) moiety of L-363,301, was synthesized in two steps by an enantioselective multicomponent reaction using (-)-8-phenylmenthol as a chiral auxiliary. The resulting peptide cyclo[cbetaAA(1)-Tyr(2)-D-Trp(3)-Nle(4)-Thr(Trt)(5)] (Trt = triphenylmethyl) shows high antiproliferative effects in an in vitro assay with A431 cancer cells. The same peptide without the Trt group does not reveal any biological activity, whereas L-363,301 and closely related hexapeptides show only minor activity. By comparison of the solution structure of cyclo[cbetaAA(1)-Tyr(2)-D-Trp(3)-Nle(4)-Thr(Trt)(5)] with the structure of l-363,301, a nearly perfect match of the betaII'-turn region with d-Trp in the i + 1 position was observed. The cyclic beta-amino acid cbetaAA is likely needed for the bioactive conformation of the peptide.
authors.affiliation: Lehrstuhl für Organische Chemie und Biochemie II, Technische Universität München, Lichtenbergstrasse 4, 85747 Garching, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Sukopp
authors.forename: Richard
authors.initials: R
authors.lastname: Schwab
authors.forename: Luciana
authors.initials: L
authors.lastname: Marinelli
authors.forename: Eric
authors.initials: E
authors.lastname: Biron
authors.forename: Markus
authors.initials: M
authors.lastname: Heller
authors.forename: Edit
authors.initials: E
authors.lastname: Várkondi
authors.forename: Akos
authors.initials: A
authors.lastname: Pap
authors.forename: Ettore
authors.initials: E
authors.lastname: Novellino
authors.forename: György
authors.initials: G
authors.lastname: Kéri
authors.forename: Horst
authors.initials: H
authors.lastname: Kessler
mesh_terms: D000598:Amino Acids, Cyclic / Q000737:chemistry*; D000970:Antineoplastic Agents / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D045744:Cell Line, Tumor; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D010446:Peptide Fragments / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology; D010456:Peptides, Cyclic / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D013004:Somatostatin / Q000031:analogs & derivatives* / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D013237:Stereoisomerism; D013329:Structure-Activity Relationship
chemical_list: D000598:Amino Acids, Cyclic; D000970:Antineoplastic Agents; D010446:Peptide Fragments; D010456:Peptides, Cyclic; C040704:cyclo(Pro-Phe-Trp-Lys-Thr-Phe); D013004:Somatostatin