Amino acids and peptides. XLV. Analogues of oxytocin with O-ethyltyrosine, p-methylphenylalanine, and p-ethylphenylalanine replacing tyrosine

Oxytocin and Its Analogs, Methyl-Substituted in Ortho-, Meta- or Para- Position of Aromatic Ring of Phenylalanine in Position 2: NMR Study and Biological Activities

“…Very small values of coefficients ∆NH/∆T of Tyr(MePhe) 2 NH and Asn 5 NH (≈ -1 ppb/deg) indicate a stabilization of the cyclic part of the molecules by two Hbonding (as indicated in Figure 1) in a similar way as it was suggested for deamino-oxytocin from NMR and X-ray data [14,15]. The acyclic part of the molecule is apparently flexible and its protons do not show any NOE contacts to the cyclic part.…”

“…The synthesis and biological qualities of several oxytocin analogues with minor modification in position 2 of the peptide chain are described in the literature [1][2][3][4]. Among these analogues, four are very interesting from the structure activity relationship, (see Scheme 1).…”

The Action of Oxytocin and Synthetic Analogues on the Isolated Mammary-Gland Myoepithelium of the Lactating Rat; Effect of Some Ions

“…The oxytocin analogues were derivatives with the isoleucine in position 3 of the peptide chain replaced by valine (Val3), leucine (Leu3), norleucine (Nie3), norvaline (Nva3), and alloisoleucine (alle3); with the tyrosine in position 2 replaced by 0methyltyrosine (Tyr(Me)2), phenylalanine (Phe2),^-methylphenylalanine (Phe(p-Me)2), p-ethylphenylalanine (Phe(^)-Et)2), and O-ethyltyrosine (Tyr(Et)2) ; and with the peptide chain of oxytocin extended at the amino end by a leucine or a phenylala¬ nine residue (leucyl-oxytocin and phenylalanyl-oxytocin ; Leu-Cys1-and Phe-Cys1oxytocin). The compounds were synthetized at the Institute of Organic Chemistry and Biochemistry of the Czechoslovak Academy of Science (Nesvadba et al 1963;Jost, Rudinger & Sorm, 1963a, b;Zhuze et al 1964; Kasafírek, Jost, Rudinger & Sorm, 1965), purified by countercurrent distribution and characterized by analysis. They were dissolved in 0-25 % acetic acid (usually at the concentration of 1 mg./ml.)…”

“…1 Bisset (1964). k Revised from the preliminary figures in the preparative paper (Zhuze et al 1964). Bisset (1964) records a potency of 8-4 i.u./mg.…”

“…The isolated strip of rat mammary gland introduced by Rydén & Sjöholm (1962) appeared to be a more suitable counterpart to the rat uterine muscle for this purpose. Having recently studied the action of a series of oxytocin analogues on the rat uterus (Rudinger & Krejci, 1962;Nesvadba, Honzl & Rudinger, 1963; Zhuze, Jost, Kasafirek & Rudinger, 1964; Krejci, Polácek & Rudinger, 1966;Beránková-Ksandrová, Bisset, Jost, Krejci, Pliska, Rudinger, Rychlík & Sorm, 1966) we thought it of interest to examine the action of selected representatives of this series on the mammary-gland strip. So far, only three oxytocin analogues appear to have been examined for their effect on this preparation (Bisset, 1964;Beránková-Ksandrová et al 1966).…”