Preferred Conformations of Peptides Containing tert-Leucine, a Sterically Demanding, Lipophilic α-Amino Acid with a Quaternary Side-Chain Cβ Atom
✍ Scribed by Fernando Formaggio; Chiara Baldini; Vittorio Moretto; Marco Crisma; Bernard Kaptein; Quirinus B. Broxterman; Claudio Toniolo
- Publisher
- John Wiley and Sons
- Year
- 2005
- Tongue
- English
- Weight
- 196 KB
- Volume
- 11
- Category
- Article
- ISSN
- 0947-6539
No coin nor oath required. For personal study only.
✦ Synopsis
Abstract
Terminally protected homopeptides of tert‐leucine, from the dimer to the hexamer, co‐oligopeptides of tert‐leucine in combination with α‐aminoisobutyric acid or glycine residues up to the hexamer level, and simple dipeptides representing known scaffolds for catalysts in asymmetric organic reactions were prepared by solution methods and fully characterized. The results of conformation analysis, performed by use of FT‐IR absorption, NMR, CD, and X‐ray diffraction techniques, indicate that this hydrophobic α‐amino acid with tetrasubstitution at the C^β^ atom is structurally versatile. We show that it prefers extended or semiextended conformations, but can also be accommodated in folded structures, provided that these are biased by the presence of helicogenic residues. The current large‐scale production of Tle, combined with its conformational preferences unravelled in this work, should make this bulky, hydrophobic, C^α^‐trisubstituted α‐amino acid a regular building block of any strategy seeking to tailor peptides with improved catalytic and pharmacological properties.