Characterization of tautomeric limonoids from the fruits of Melia toosendan

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• 作者：Sheng Su ; Liqin Shen ; Yan Zhang ; Jiangyun Liu ; Jinna Cai ; Lili Hao ; Yuling Feng ; Shilin Yang
• 关键词：Limonoid ; Melia toosendan ; Nimbolinin ; Tautomerism
• 刊名：Phytochemistry Letters
• 出版年：2013
• 出版时间：August, 2013
• 年：2013
• 卷：6
• 期：3
• 页码：418-424
• 全文大小：862 K

文摘

Four nimbolinin-type limonoids, 12¦Á/¦Â-1-O-tigloyl-1-O-deacetyl-nimbolinin B (1), 1-deacetylnimbolinin B (2), nimbolinin B (3) and nimbolinin A (4), were isolated from the fruits of Melia toosendan. 1 was a new compound and existed as a mixture of a pair of tautomers, 12¦Á- (1a) and 12¦Â- (1b). The structures of both tautomers were fully determined by extensive spectroscopic methods including UV, IR, NMR and ESI-MS. Tautomeric behaviors and their relative molar ratios in compounds 1-4 were further investigated using optical rotation, TLC, ¹H NMR and HPLC. Equilibrium equation of nimbolinin was proposed accordingly, with 12¦Á- and 12¦Â-isomers interchanging via a 12-hemiacetal intermediate.