Synthetic 6-aryl-2-hydroxy-6-ketohexa-2,4-dienoic acid substrates for C-C hydrolase BphD: investigation of a general base catalytic mechanism.
Synthetic 6-aryl-2-hydroxy-6-ketohexa-2,4-dienoic acid substrates for C-C hydrolase BphD: investigation of a general base catalytic mechanism.
复制标题
C-C 水解酶 BphD 的合成 6-芳基-2-羟基-6-酮六-2,4-二烯酸底物：一般碱催化机制的研究。
DOI：
10.1039/b410322j
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发表时间：
2004
影响因子：
3.2
通讯作者：
T. Bugg
中科院分区：
文献类型：
--
作者：
Damian M Speare;S. M. Fleming;Martin Beckett;Jian;T. Bugg
利用Heck偶联策略，建立了细菌间位裂解途径上2-羟基-6-酮己-2，4-二烯酸中间体的化学合成。3-溴-2-乙酰氧基丙烯酸乙酯与1-芳基乙烯基缩酮或1-芳基烯丙醇的偶联以70-90%产率进行。Heck与烷基乙烯基缩酮的偶联也是成功的，允许合成烷基取代的环分裂中间体。以合成的裂环中间体为原料，研究了假单胞菌LB 400的C-C水解酶BphD催化的酶促反应。通过C-C水解酶BphD将还原底物类似物2，6-二羟基-6-苯基己-2，4-二烯酸酶促加工成苯甲醛，这与涉及水的一般碱催化攻击以得到偕二醇中间体的催化机理一致，而与亲核机理不一致。针对BphD测定了一系列对位取代的2-羟基-6-酮基-6-苯基己-2，4-二烯酸底物，并且导出的Hammett图（rho=-0.71）与C-C裂解的过渡态中的离去碳负离子一致。
A chemical synthesis of the 2-hydroxy-6-ketohexa-2,4-dienoic acid intermediates on bacterial meta-cleavage pathways has been established, using a Heck coupling strategy. Coupling of ethyl 3-bromo-2-acetoxyacrylate with 1-aryl vinyl ketals or 1-aryl allylic alcohols proceeded in 70-90% yield. Heck coupling with an alkyl vinyl ketal was also successful, allowing the synthesis of an alkyl-substituted ring fission intermediate. The synthetic ring fission intermediates were used to investigate the enzymatic reaction catalysed by C-C hydrolase BphD from Pseudomonas LB400. A reduced substrate analogue 2,6-dihydroxy-6-phenylhexa-2,4-dienoic acid was processed enzymatically to benzaldehyde by C-C hydrolase BphD, consistent with a catalytic mechanism involving general base-catalysed attack of water to give a gem-diol intermediate, and not consistent with a nucleophilic mechanism. A series of para-substituted 2-hydroxy-6-keto-6-phenylhexa-2,4-dienoic acid substrates were assayed against BphD, and the derived Hammett plot (rho=-0.71) is consistent with a departing carbanion in the transition state for C-C cleavage.