δ-Peptide Analogues of Pyranosyl-RNA, Part 2, Nucleo-δ-peptides Derived from Conformationally Constrained Nucleo-δ-amino Acids: NMR Study of the Duplex Formed by Self-pairing of the (1'S,2',4'S)-(phba)-Nucleo-δ-peptide-(AATAT)

delta-Peptides of the type described in this series are analogues of pyranosyl-RNAs with respect to their capability of base pairing in the Watson-Crick mode. An NMR-based conformational analysis of the title duplex at various levels of sophistication has been carried out: at the level of qualitative conformational analysis, at that of quantitative conformational analysis, and at that of structure calculation using MD search of torsion-angle space. The duplex formed has an antiparallel arrangement of two complementary strands and is stabilized by Watson-Crick base pairing, as well as by interstrand pi-pi base stacking, dangling-end nucleobase interaction included.