The crystal-state conformations of three protected tripeptides, four tetrapeptides, and one pentapeptide, heavily based on the chiral C-alpha-methylated alpha-amino acids Iva, (alpha Me)Nva, and (Me) Val, were assessed by X-ray diffraction analyses. The eight peptide sequences are as follows: Z-((D)-Iva)(2)-(D)-Val-OMe, Z-(D)-Iva-(L)-Iva-Gly-OtBu, Z-(L)-Pro-(D)-Iva-(L)-Iva-Gly-OtBu, Z-(L)-Pro-(L)-Iva-(D)-Iva-Gly-OtBu, Z-Aib-[(L)-(alpha Me)Nva](2)-OtBu, Ac-[(L)-(alpha Me)Val](3)-D-(alpha Me)Val-OtBu, Z-[L-(alpha Me)Val](4)-OH, and Z-(L)-Ala-[(L)-(alpha Me)Nva](4)-OtBu. Two independent molecules were observed in the asymmetric units of Z-(D)-Iva-(L)-Iva-Gly-OtBu and Z-Aib-[(L)-(alpha Me)Nva](2)-OtBu, while three independent molecules were seen in Z-(L)-Ala-[(L)-(alpha Me)Nva](4)-OtBu.
Turn stabilization in short peptides by C-alpha-methylated alpha-amino acids
MORETTO, ALESSANDRO;DE ZOTTI, MARTA;FORMAGGIO, FERNANDO;TONIOLO, CLAUDIO
2005
Abstract
The crystal-state conformations of three protected tripeptides, four tetrapeptides, and one pentapeptide, heavily based on the chiral C-alpha-methylated alpha-amino acids Iva, (alpha Me)Nva, and (Me) Val, were assessed by X-ray diffraction analyses. The eight peptide sequences are as follows: Z-((D)-Iva)(2)-(D)-Val-OMe, Z-(D)-Iva-(L)-Iva-Gly-OtBu, Z-(L)-Pro-(D)-Iva-(L)-Iva-Gly-OtBu, Z-(L)-Pro-(L)-Iva-(D)-Iva-Gly-OtBu, Z-Aib-[(L)-(alpha Me)Nva](2)-OtBu, Ac-[(L)-(alpha Me)Val](3)-D-(alpha Me)Val-OtBu, Z-[L-(alpha Me)Val](4)-OH, and Z-(L)-Ala-[(L)-(alpha Me)Nva](4)-OtBu. Two independent molecules were observed in the asymmetric units of Z-(D)-Iva-(L)-Iva-Gly-OtBu and Z-Aib-[(L)-(alpha Me)Nva](2)-OtBu, while three independent molecules were seen in Z-(L)-Ala-[(L)-(alpha Me)Nva](4)-OtBu.Pubblicazioni consigliate
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