SYNTHESIS, CHARACTERIZATION, IN SILICO OPTIMIZATION, AND CONFORMATIONAL STUDIES OF METHYL 4-O-PIVALOYL-αL-RHAMNOPYRANOSIDES

Mohammed Mahbubul, Matin and Mohammad, Ibrahim and Tasnim Rahman, Anisa and Md. Rezaur, Rahman (2022) SYNTHESIS, CHARACTERIZATION, IN SILICO OPTIMIZATION, AND CONFORMATIONAL STUDIES OF METHYL 4-O-PIVALOYL-αL-RHAMNOPYRANOSIDES. Malaysian Journal Of Science, 41 (1). pp. 91-105. ISSN 2600-8688

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Abstract

Considering promising biological activities of natural and synthetic rhamnopyranoside esters, we have synthesized several methyl 4-O-pivaloyl-α-Lrhamnopyranosides via selective 2,3-O-acetonide protection of methyl α-Lrhamnopyranoside (4) followed by C-4 pivaloylation, and deprotection. The synthesized 4-O-pivaloate 7 and its 2,3-di-O-esters 8a-e are characterized by spectroscopy and are optimized by using density functional theory (DFT). The free energy and bond angles thus calculated are used to establish the probable conformation(s). The 2,3-O-acetonide protected rhamnopyranosides 5-6 are found to be slightly distorted from the regular 1C4 conformation, and exist between the chair and twist-boat (skew) conformation while other pivaloyl esters 7-8a-e exist in regular 1C4 chair conformation.

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