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Stepwise solution syntheses of the homo-oligomers Boc-(Asn)n-NHCH3 (n = 1–5; I1–5), Boc-{[GlcNAc(Ac)3β]Asn}n-NHCH3 (n = 1–8; II1–8), and Boc-[(GlcNAcβ)Asn]n-NHCH3 (n = 1–8; III1–8) are described. Members of the series III were obtained by deacetylation of the corresponding members of the series II. The conformational preferences of the N-protected homo-peptides of the three series were investigated by spectroscopic techniques. ¹H-NMR measurements were carried out in various solvents; the CD spectra were recorded in water, aqueous SDS and TFE. The poor solubility of the oligomers of the three series prevented FT-IR measurements in solution. NMR and IR measurements indicate the existence of unordered structures containing some γ-turns in the carbohydrate-free oligomers and the presence of β-turns in the glycosylated oligopeptides, whether acetylated or not. The CD spectra do not indicate the presence of organized structures. The sugar moieties apparently do not have a structure-inducing effect on the asparagine homo-oligomer main chain. Copyright © 2002 European Peptide Society and John Wiley & Sons, Ltd.

Stepwise solution syntheses of the homo‐oligomers Boc‐(Asn)n‐NHCH3(n= 1–5; I1–5), Boc‐{[GlcNAc(Ac)3β]Asn}n‐NHCH3(n= 1–8; II1–8), and Boc‐[(GlcNAcβ)Asn]n‐NHCH3(n= 1–8; III1–8) are described. Members of the series III were obtained by deacetylation of the corresponding members of the series II. The conformational preferences of the N‐protected homo‐peptides of the three series were investigated by spectroscopic techniques. 1H‐NMR measurements were carried out in various solvents; the CD spectra were recorded in water, aqueous SDS and TFE. The poor solubility of the oligomers of the three series prevented FT‐IR measurements in solution. NMR and IR measurements indicate the existence of unordered structures containing some γ‐turns in the carbohydrate‐free oligomers and the presence of β‐turns in the glycosylated oligopeptides, whether acetylated or not. The CD spectra do not indicate the presence of organized structures. The sugar moieties apparently do not have a structure‐inducing effect on the asparagine homo‐oligomer main chain. Copyright © 2002 European Peptide Society and John Wiley & Sons, Ltd.

Three linear bradykinin (BK) analogues, Lys-Lys-BK, Nle-Lys-BK and Lys-Nle-BK and their head-to-tail cyclic analogues, along with cyclo-Nle-Nle-BK and cyclo-Lys-Lys-[Trp5]BK, were synthesized and tested on an isolated rat duodenum preparation. All kinins, except the [Trp5]-analogue, cause relaxation with EC50values in the picomolar range. The most potent linear analogue (Lys-Nle-BK) is about 40 times more active than BK and the most potent cyclic kinin (cyclo-Nle-Lys-BK) is about 6 times more active. Present results suggest that the significant potency of cyclo-Lys-Lys-BK, the earlier most potent cyclic kinin which is only a little less potent than linear BK, depends on the ring size rather than on the presence of the extra basic residues.

Three linear bradykinin (BK) analogues, Lys-Lys-BK, Nle-Lys-BK and Lys-Nle-BK and their head-to-tail cyclic analogues,along with cyclo-Nle-Nle-BK and cyclo-Lys-Lys-[Trp5]BK, weresynthesized and tested on an isolated rat duodenum preparation.All kinins, except the [Trp5]-analogue, cause relaxation withEC50values in the picomolar range. The most potent linearanalogue (Lys-Nle-BK) is about 40 times more active than BK andthe most potent cyclic kinin (cyclo-Nle-Lys-BK) is about 6 timesmore active. Present results suggest that the significant potencyof cyclo-Lys-Lys-BK, the earlier most potent cyclic kinin which isonly a little less potent than linear BK, depends on the ringsize rather than on the presence of the extra basic residues.

Stepwise solution syntheses are described of the homo-oligomers Z-(Thr)n-NHCH3 (n=1–4, I1–4), Z-{[Gal(Ac)4β]Thr}n-NHCH3(n=1–5, II1–5) and Z-[(Galβ)Thr]n-NHCH3 (n=1−5, III1–5). Members of the III1–5 series were obtained by de-acetylation of the corresponding oligomers of the II1–5 series. The conformational preferences of the terminally protected homo-peptides of the three series were investigated by FT-IR absorption spectroscopy both in the solid state and in CDCl3 solution, at various concentrations. Proton NMR measurements in CDCl3 and in DMSO-d6 were also carried out and the effect of temperature variation on the chemical shifts of amide protons was determined in DMSO-d6 (range 298–335 K) and in CDCl3 (range 298–320 K). CD spectra were recorded in water and in TFE. Solubility problems prevented measurements in CDCl3 solution for Z-(Thr)4-NHCH3 and for the entire III1–5 series. The existence of unordered structures in the carbohydrate-free oligomers and of more or less extended, organized structures in the glycosylated derivatives is indicated by the NMR and IR measurements. The sugar moieties apparently show a structure-inducing effect on the peptide chain. ©1998 European Peptide Society and John Wiley & Sons, Ltd.

Stepwise solution syntheses are described of the homo‐oligomers Z‐(Thr)n‐NHCH3(n=1–4, I1–4), Z‐{[Gal(Ac)4β]Thr}n‐NHCH3(n=1–5, II1–5) and Z‐[(Galβ)Thr]n‐NHCH3(n=1−5, III1–5). Members of the III1–5series were obtained by de‐acetylation of the corresponding oligomers of the II1–5series. The conformational preferences of the terminally protected homo‐peptides of the three series were investigated by FT‐IR absorption spectroscopy both in the solid state and in CDCl3solution, at various concentrations. Proton NMR measurements in CDCl3and in DMSO‐d6were also carried out and the effect of temperature variation on the chemical shifts of amide protons was determined in DMSO‐d6(range 298–335 K) and in CDCl3(range 298–320 K). CD spectra were recorded in water and in TFE. Solubility problems prevented measurements in CDCl3solution for Z‐(Thr)4‐NHCH3and for the entire III1–5series. The existence of unordered structures in the carbohydrate‐free oligomers and of more or less extended, organized structures in the glycosylated derivatives is indicated by the NMR and IR measurements. The sugar moieties apparently show a structure‐inducing effect on the peptide chain. ©1998 European Peptide Society and John Wiley & Sons, Ltd.

A series of longer analogues of the C-peptide of RNAse A has been synthesized with the aim of assessing the helix induction potential in water of α-methyl, α-amino acids at the N-terminus of the chain. The circular dichroism data indicate that one isovaline residue is effective in increasing the helix content of the 13-residue peptide by about 7%.

A series of longer analogues of the C-peptide of RNAse A has been synthesized with the aim of assessing the helix induction potential in water of α-methyl, α-amino acids at the N-terminus of the chain. The circular dichroism data indicate that one isovaline residue is effective in increasing the helix content of the 13-residue peptide by about 7%.

For Abstract see ChemInform Abstract in Full Text.