# Synthesis and conformations of stereochemically restricted analogs of $Leu_5-enkephalinamide$: substitution of a -aminoisobutyric acid and 1-aminocyclopentane-1-carboxylic acid at positions 2 and 3

Kishore, R and Balaram, P (1984) Synthesis and conformations of stereochemically restricted analogs of $Leu_5-enkephalinamide$: substitution of a -aminoisobutyric acid and 1-aminocyclopentane-1-carboxylic acid at positions 2 and 3. In: Indian Journal of Chemistry, Sect. B: Organic Chemistry including Medicinal Chemistry, 23 (12). pp. 1137-1144.

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## Abstract

Title peptides $H-Tyr-Aib-Gly-Phe-Leu-NH_2$ $(I, Aib = NHCMe_2CO)$, H-Tyr-Gly-Aib-Phe-Leu-$NH_2$ (II), H-Tyr-Aib-Aib-Phe-Leu-$NH_2$ (III), $H-Tyr-Acc_5-Gly-Phe-Leu-NH_2$ (IV, Acc=1-aminocyclopentane-1-carboxylic acid residue), $H-Tyr-Gly-Acc_5-Phe-Leu-NH_2$ (V), and $H-Tyr-Acc_5-Acc_5-Phe-Leu-NH_2$ (VI) were prepared by conventional solution methods and they were characterized by 270 MHz $^1H$ NMR and reversed-phase high-performance liquid chromatography. NMR data showed intramolecular H bonding in $(CD_3)_2SO$. I and IV adopt a b-turn structure centered at positions 2 and 3, whereas II and V have \beta-turns at positions 3 and 4. III and VI favor consecutive \beta-turn conformations.

Item Type: Journal Article http://www.niscair.res.in/sciencecommuni... Copyright of this article belongs to Council of Scientific & Industrial Research. Division of Biological Sciences > Molecular Biophysics Unit 07 May 2008 27 Aug 2008 13:21 http://eprints.iisc.ernet.in/id/eprint/13838