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Publication Abstract from PubMed

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 H2N-D-Leu-D-Phe-2-Abz-D-Ala-COOH (1) reveals a novel planar peptidomimetic beta-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 2-Abz containing CTP 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 solution conformation of 3.

Crystal and NMR Structures of a Peptidomimetic beta-turn which provides facile synthesis of 13-membered Cyclic Tetrapeptides.,Cameron AJ, Squire CJ, Edwards PJB, Harjes E, Sarojini V Chem Asian J. 2017 Nov 2. doi: 10.1002/asia.201701422. PMID:29098772^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.