Synthesis and Biological Activities of Arginine-Vasopressin Analogues with Reactive Groups

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Abstract
The synthesis and biological activities of Arg-vasopressin [VP] analogs are described, where p-azido-L-phenylalanine [Phe(pN3)] or p-(bromoacetylamino)-L-phenylalanine [Phe-(pNHCOCH2Br)] replace Tyr2 or Phe3. The hormone analogs are prepared via precursors containing p-aminophenylalanine [Phe(pNH2)] in position 2 or 3. During peptide synthesis the p-amino group of [Phe(pNH2)] is protected by the tert-butyloxycarbonyl or the benzyloxycarbonyl group, the side chains of Cys and Arg by the acetamidomethyl residue and the tosyl group, respectively. The amino and guanidino protecting groups are removed from the nonapeptides by trifluoromethanesulfonic acid yielding the S-protected derivatives which are cyclized by means of I. The ring closure by disulfide formation is confirmed by Edman degradation, CD [circular dischroism] and 1H-NMR spectroscopy. Modifications at the p- and .alpha.-amino groups result in [Phe(pN3)2]-VP, [Phe(pNHCOCH2Br)2]VP, N.alpha.-dansyl-[Phe(pN3)2]VP, [Phe2,Phe(pN3)3]VP and [Phe2,Phe(pNHCOCH2Br)3]VP. The analogs modified only in position 2, [Phe(pN3)2]VP and [Phe(pNHCOCH2Br)2]VP stimulate the adenylate cyclase derived from bovine kidney inner medulla to similar maximal velocities as Arg VP and show high apparent affinites for enzyme activation. The N.alpha.-dansyl derivative and the analogs with reactive groups in position 3 have reduced maximal velocities and apparent affinities for VP-sensitive adenylate cyclase. The derivatives with reactive groups in position 2 are useful for the labeling of VP receptors in plasma membranes and for studies of covalent hormone-receptor complexes.

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