Crystal and molecular structure of N?-acetyl-aza-?'-homo-l-valine methylamide

A Computational Study of Partially Modified Retro-Inverso Valine Dipeptides: Effect of the Side Chain on the Conformational Preferences of Malonyl and gem-Diamino Residues

“…The structure of 13 was determined by Kemme et al 17 20 years ago using X-ray crystallography. The dihedral angles of the resulting conformation were φ 1 , φ 2 ) 113°, -105°.…”

“…For 13 the comparison with experiment is more difficult because the final agreement factor R for the three compounds containing the gem-diamino residue was too large. [17][18][19] 6 and 7, providing standard deviations of 0.012 Å and 0.7° (12) and 0.011 Å and 0.8°(13).…”

Partially Modified Retro-Inverso Peptides: Development, Synthesis, and Conformational Behavior

“…77,78 The net effect of this modification is to add an amino group between C R and C′ of an R-amino acid residue thus generating a gem-diaminoalkyl residue and an adjacent ureide linkage in the peptide backbone. 77,79,80 Various angiotensin analogues incorporating aza-R′homoamino acids of natural and inverted configuration have been synthesized, for example Figure 7. [77][78][79][81][82][83][84] Chorev and Goodman exhaustively reviewed the field of PMRI peptides in 1993 85 and further reviewed developments in enantio-, retro-, and retro-inverso peptides and proteins in 1995.…”

“…At about the same time as the PMRI peptide concept emerged, Ancans and co-workers developed a related mode of peptide modification involving the incorporation of “aza-α‘-homoamino acids”. , The net effect of this modification is to add an amino group between C α and C‘ of an α-amino acid residue thus generating a gem- diaminoalkyl residue and an adjacent ureide linkage in the peptide backbone. ,, Various angiotensin analogues incorporating aza-α‘-homoamino acids of natural and inverted configuration have been synthesized, for example Figure . − ,−

7 [Asn 1 ,aza-α‘-homoTyr 4 ,Val 5 ]angiotensin II, cf. Figure a.

…”

Extended form of a retro-inverso peptide stabilized by ?-sheet unidirectional H-bonds: Crystallographic and NMR evidence

“…A relatively small number of crystal structures of retro‐peptides has been reported. Two helical32, 33 and seven extended20, 34–39 conformations have been found in crystal structures containing gem ‐diamino alkyl moieties, while five helical40–43 and three extended42, 44, 45 conformations have been found in crystal structures containing malonyl residues. The local minima, derived from energy calculations, and the backbone torsion angles, determined from x‐ray crystal structures of gem ‐diamino alkyl and malonyl residue containing peptides, have been summarized in a recent review 46…”