Aza-peptides II. X-Ray structures of aza-alanine and aza-asparagine-containing peptides |
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Authors: | FR D RIC ANDR ,GUY BOUSSARD,DANIEL BAYEUL,CLAUDE DIDIERJEAN,ANDR AUBRY,MICHEL MARRAUD |
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Affiliation: | FRÉDÉRIC ANDRÉ,GUY BOUSSARD,DANIEL BAYEUL,CLAUDE DIDIERJEAN,ANDRÉ AUBRY,MICHEL MARRAUD |
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Abstract: | In order to determine the structural consequences of the Nx/CxH exchange in aza-peptides, we have solved the crystal molecular structures of some derivatives containing the aza-analogue of asparagine [Z-AzAsn(Me)-NMe2 (1), Z-AzAsn(Me)-Pro-NHiPr (2) and Piv-Pro-AzAsn(Me)-NHiPr (5), aspartic acid [Z-AzAsp(OEt)-Pro-NHiPr (3) and alanine (Boc-AzAla-Pro-NHiPr (4), by using X-ray diffraction. They reveal that the α-nitrogen accommodates a pyramidal (1–4) or planar (5) structure depending on the sequence. When pyramidal, the α-nitrogen assumes the R (D-like) chiralily. All of the derivatives but 1 adopt either a β1-folded (2–4) or βII-folded (5) structure in which the (AzAsn)NδH bond is intramolecularly hydrogen-bonded to the α-nitrogen. © Munksgaard 1997. |
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Keywords: | aza-alanine aza-asparagine aza-peptides crystal molecular structure pseudopeptide X-ray diffraction |
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