Conformational Analysis of Peptides Containing Enantiomerically Pure α-Methylasparagine: Correspondence Between Computed and Solid State Structures

Asparagine has a high frequency of occurrence in β-turns. We have recently completed an asymmetric synthesis of α-methylasparagine suitably protected for incorporation into polypeptides, and report herein the synthesis and structure of dipeptide Ac-Ala-(Me)Asn-NHMe (1). The synthesis proceeds through the corresponding α-methylasparagine succinimide derivative. The three-dimensional structure of the dipeptide around the α,α-dialkylated α-amino acid is compared to that predicted for Ac-(Me)Asn-NHMe.