Structural versatility of peptides from Cα,α-disubstituted glycines: Preferred conformation of the Cα,α-diphenylglycine residue

✍ Scribed by M. Crisma; G. Valle; G. M. Bonora; E. De Menego; C. Toniolo; F. Lelj; V. Barone; F. Fraternal

• Publisher: Wiley (John Wiley & Sons)
• Year: 1990
• Tongue: English
• Weight: 751 KB
• Volume: 30
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/bip.360300103

✦ Synopsis

Abstract

The preferred conformation of the C^α,α^‐diphenylglycine residue was determined in simple derivatives and dipeptides. The dipeptides were synthesized by the 5(4__H__)‐oxazolone (from the N‐para‐bromobenzoylated amino acid) method. This activated intermediate and a reaction by‐product, para‐bromobenzoylbenzhydrylamine, were characterized inter alia by x‐ray diffraction. Conformational energy calculations on the C^α,α^‐diphenylglycine mono‐peptide, Ac‐Døg‐NHMe, indicate that this C^α,α^‐symmetrically disubstituted residue is conformationally restricted and that its minimum energy conformation falls in the fully extended (C~5~) region. The results of the theoretical analysis are in agreement with the solution and crystal‐state structural tendency of mClAc‐Døg‐OH, Z‐Døg‐O__t__Bu, __p__BrBz‐Døg‐Gly‐OMe and its tert‐butyl ester analogue, determined by ir absorption, ^l^H‐nmr, and x‐ray diffraction, and also described in this work. The implications for the use of the Døg residue in designing conformationally constrained analogues of bioactive peptides are briefly discussed.