Conformations of β-amino acid residues in peptides: X-ray diffraction studies of peptides containing the achiral residue 1-aminocyclohexaneacetic acid, β<SUP>3,3</SUP>Ac<SUB>6</SUB>c
- Vasudev, Prema G.
- Rai, Rajkishor
- Shamala, Narayanaswamy
- Balaram, Padmanabhan
DOIAbstract
The conformational preferences of the 3,3-disubstituted β-amino acid residue, 1-aminocyclohexaneacetic acid (β<SUP>3,3</SUP>Ac<SUB>6</SUB>c) have been investigated by determining the crystal structures of the parent amino acid, the hydrochloride derivative, 10 protected derivatives and di and tripeptides. The symmetrical cyclohexyl substituent at the β -position restricts the values of the torsion angles Φ(N-Cβ) and θ(Cβ-C<SUP>α</SUP>) to approximately gauche values (±60°). Relatively few intramolecularly hydrogen bonded conformations are observed. In the dipeptide Boc-β<SUP>3,3</SUP>Ac<SUB>6</SUB>c-β<SUP>3,3</SUP>Ac<SUB>6</SUB>c-NHMe a C<SUB>6</SUB> hydrogen bond is observed. In P...
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