Crystal and NMR Structures of a Peptidomimetic ?-Turn That Provides Facile Synthesis of 13-Membered Cyclic Tetrapeptides.
Related Articles Crystal and NMR Structures of a Peptidomimetic ?-Turn That Provides Facile Synthesis of 13-Membered Cyclic Tetrapeptides.
Chem Asian J. 2017 Dec 14;12(24):3195-3202
Authors: Cameron AJ, Squire CJ, Edwards PJB, Harjes E, Sarojini V
Abstract
Herein we report the unique conformations adopted by linear and cyclic tetrapeptides (CTPs) containing 2-aminobenzoic acid (2-Abz) in solution and as single crystals. The crystal structure of the linear tetrapeptide H2 N-d-Leu-d-Phe-2-Abz-d-Ala-COOH (1) reveals a novel planar peptidomimetic ?-turn stabilized by three hydrogen bonds and is in agreement with its NMR structure in solution. While CTPs are often synthetically inaccessible or cyclize in poor yield, both 1 and its N-Me-d-Phe analogue (2) adopt pseudo-cyclic frameworks enabling near quantitative conversion to the corresponding CTPs 3 and 4. The crystal structure of the N-methylated peptide (4) is the first reported for a CTP containing 2-Abz and reveals a distinctly planar 13-membered ring, which is also evident in solution. The N-methylation of d-Phe results in a peptide bond inversion compared to the conformation of 3 in solution.
PMID: 29098772 [PubMed - indexed for MEDLINE]
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