Synthesis and Structure – Activity Investigation of Novel

Abstract

Symbols and abbreviations are in accordance with the recommendations of the IUPAC-IUB Commission on Biochemical Nomenclature (Eur. J. Biochem. 1989; 180: A9–A11). All amino acids are in the L-configuration unless otherwise noted. Other abbreviations used are; AVP, arginine vasopressin; D-Tyr(Et), O-ethyl-D-tyrosine; D-Tyr(Me), O-methyl-D-tyrosine; L-Tyr(Et), O-ethyl-L-tyrosine; MeArg, N-methyl-arginine; Eda, ethylendiamine; desGly, desglycine [carboxy terminus is ArgNH2 or LysNH2]; desGly(NH2), desglycineamide [carboxy terminus is ArgOH; Sar, sarcosine; Eda?Tyr, Eda retro-L-tyrosine; d(CH2)5[D-Tyr(Et)2, Val4]AVP, [1-(?-mercapto-?,?-pentamethylenepropi- onic acid), 2-O-ethyl-D-tyrosine, 4-valine] arginine vasopressin; d(CH2)5[D-Tyr(Et)2, Arg3, Val4]AVP (A), [1-(?-mercapto-?,?-pentamethylene- propionic acid),2-O-ethyl-D-tyrosine, 3-arginine, 4-valine]arginine vasopressin; d(CH2)5[D-Tyr(Et)2, Lys3, Val4]AVP (B), Lys3 analog of A; d(CH2)5[D-Tyr(Et)2, Arg3, Val4, Tyr-NH2 9]AVP (C), Tyr-NH2 9 analog of A; d(CH2)5[D-Tyr(Et)2, Lys3, Val4, Tyr-NH2 9]AVP (D), Tyr-NH2 9 analog of B; d(CH2)5[D-Tyr(Me)2, Arg3, Val4]AVP, D-Tyr-(Me)2 analog of A; d(CH2)5[L-Tyr(Et)2, Arg3, Val4]AVP, L-Tyr(Et)2, analog of A; d(CH2)5[D-Tyr(Et)2, Orn3, Val4]AVP, Orn3 analog of A; d(CH2)5[D-Tyr(Et)2, MeArg3, Val4]AVP, N-Me-Arg3 analog of A; d(CH2)5[D-Tyr(Et)2, Glu3, Val4]AVP, Glu3 analog of A; d(CH2)5[D-Tyr(Et)2, Arg3, Arg4]AVP, Arg4 analog of A; d(CH2)5[D-Tyr(Et)2, Arg3, Gln4, Tyr-NH2 9]AVP, Gln4 analog of C; d(CH2)5[D- Tyr(Et)2, Arg3, Val4, Lys8, Tyr-NH2 9]AVP, Lys8 analog of C; d(CH2)5[D-Tyr(Et)2, Arg3, Val4, D-Arg8]AVP, D-Arg8 analog of A; d(CH2)5[D-Tyr(Et)2, Arg3, Val4, Eda9]AVP, Eda9 analog of A; d(CH2)5[D-Tyr(Et)2, Arg3, Val4, Arg-NH2 9]AVP, Arg-NH2 9 analog of A; d(CH2)5[D-Tyr(Et)2, Arg3, Val4, Ala-NH2 9]AVP, Ala-NH2 9 analog of A; desGly9, d(CH2)5[D-Tyr(Et)2, Arg3, Val4]AVP, desGly9 analog of A; desGly-NH2 9, d(CH2)5[D-Tyr(Et)2, Arg3, Val4]AVP, desGly-NH2 9 analog of A; d(CH2)5[D-Tyr(Et)2, Lys3, Val4, Arg-NH2 9]AVP, Arg-NH2 9 analog of B; desGly9, d(CH2)5[D-Tyr(Et)2, Lys3, Val4]AVP, desGly9 analog of B; d(CH2)5[D-Tyr(Et)2, Arg3, Val4, Sar7, Eda9]AVP, [Sar7, Eda9] analog of A; d(CH2)5[D-Tyr(Et)2, Arg3, Val4, Arg7, Eda9]AVP, [Arg7, Eda9] analog of A; d(CH2)5[D-Tyr(Et)2, Arg3, Arg7, Eda9?Tyr10]AVP, [Arg7, Eda9, retro-Tyr10] analog of A; d(CH2)5[D-Tyr(Et)2, Arg3, Arg4, Arg-NH2 9]AVP, [Arg4, Arg-NH2 9] analog of A; desGly9, d(CH2)5[D-Tyr(Et)2, Arg3, Ile4]AVP, [Ile4, desGly9] analog of A; desGly9, d(CH2)5[D-Tyr(Et)2, Arg3, Arg4]AVP, [Arg4, desGly9] analog of A; desGly9, d(CH2)5[D-Tyr(Et)2, Arg3, Val4, Arg7]AVP, [Arg7, desGly9] analog of A; desGly9, d(CH2)5[D-Tyr(Et)2, Arg3, Val4, Arg7, Lys8]AVP, [Arg7, Lys8, desGly9] analog of A; DMF, dimethylformamide; DCC, dicyclohexylcar- bodiimide; HOBt, 1-hydroxybenzotriazole; ONp, p-nitrophenylester; MeCN, acetonitrile; Boc, tert-butyloxycarbonyl; Bzl, benzyl; Tos, tosyl; AcOH, acetic acid; TFA, trifluoroacetic acid; DIEA, diisopropylethylamine; V2, antidiuretic; V1a, vasopressor; AUC, area under the vasode- pressor response curve; ND, non-detectable; Z, benzyloxycarbonyl; OFm, 9-fluorenylmethylester; 2-Cl-Z, 2-chlorobenzyloxycarbonyl; TLC, thin-layer chromatography; ESMS, electronspray mass spectrometry; HPLC, high performance liquid chromatography; SPPS, solid phase peptide synthesis; BOP, Castro’s Reagent, benzotriazole-1-yl-oxy-tris(dimethylamino)-phosphonium hexafluorophosphate; Phaa, phenyl- acetic acid; Aaa, 1-adamantaneacetic acid; Abu, ?-aminobutyric acid.vitro (no Mg2+) oxytocic (OT-receptor) assays and like the parent peptides (A–D) (Chan et al. Br. J. Pharmacol. 1998; 125: 803–811) were found to exhibit no or negligible activities in these assays. Vasode- pressor potencies were determined in anesthetized male rats with baseline mean arterial blood pressure maintained at 110–120 mmHg. The effective dose (ED), in ?g 100 g−1 i.v., required to produce a vasodepressor response of 5 cm2, area under the vasodepressor response curve (AUC) during the 5-min period following the injection of the test peptide, was determined. Therefore, the EDs measure the relative vasodepressor potencies of the hypotensive peptides. The following ED values were obtained for A–D and for peptides 1–24: A, 4.66; B, 5.75; C, 10.56; D, 11.60; 1, ?20; 2, ?30; 3, 6.78; 4, non-detectable (ND); 5, ND; 6, ?32; 7, ND; 8, 8.67; 9, ND; 10, 2.43; 11, 3.54; 12, 10.57; 13, 4.81; 14, ND; 15, 4.47; 16, 9.78; 17, 5.72; 18, 1.10; 19, 1.05; 20, 10.41; 21, 9.13; 22, ?33; 23, 3.01; 24, 1.71. A is clearly the most potent of the four original hypotensive peptides A–D. These data provide insights to which modification of A enhance, retain or abolish hypotensive potencies. Six of the new hypotensive peptides are significantly more potent than A. These are peptides 10, 11, 18, 19, 23 and 24. Peptide 19, a radioiodinatable ligand, is ten times 9 more potent than C or D. The Gln4 modification of C and the N-Me-Arg3, Glu3, D-Arg8 and desGly-NH2 modifications of A abolished hypotensive potency. By contrast, the Eda9, Arg-NH2 9, [Sar7, Eda9], [Arg7, Eda9?Tyr10], [Arg7, desGly9], [Arg7, Lys8, desGly9] modifications of A all led to enhancements of hypoten- sive potency. This initial structure–activity exploration provides useful clues to the design of (a) more potent vasodepressor peptides and (b) high affinity radioiodinatable ligands for the putative AVP vasodilating receptor. Some of the peptides here may be of value as pharmacological tools for studies on the complex cardiovascular actions of AVP and may lead to the development of a new class of anti-hypertensive agents. Copyright © 1999 European Peptide Society and John Wiley & Sons, Ltd.