Boyd Derek R, Sharma Narain D, Bowers Nigel I, Dalton Howard, Garrett Mark D, Harrison John S, Sheldrake Gary N
School of Chemistry and Chemical Engineering, Queen's University of Belfast, Belfast, UKBT9 5AG.
Org Biomol Chem. 2006 Sep 7;4(17):3343-9. doi: 10.1039/b608417f. Epub 2006 Jul 31.
Biotransformations of a series of ortho-, meta- and para-substituted ethylbenzene and propylbenzene substrates have been carried out, using Pseudomonas putida UV4, a source of toluene dioxygenase (TDO). The ortho- and para-substituted alkylbenzene substrates yielded, exclusively, the corresponding enantiopure cis-dihydrodiols of the same absolute configuration. However, the meta isomers, generally, gave benzylic alcohol bioproducts, in addition to the cis-dihydrodiols (the meta effect). The benzylic alcohols were of identical (R) absolute configuration but enantiomeric excess values were variable. The similar (2R) absolute configurations of the cis-dihydrodiols are consistent with both the ethyl and propyl groups having dominant stereodirecting effects over the other substituents. The model used earlier, to predict the regio- and stereo-chemistry of cis-dihydrodiol bioproducts derived from substituted benzene substrates has been refined, to take account of non-symmetric substituents like ethyl or propyl groups. The formation of benzylic hydroxylation products, from meta-substituted benzene substrates, without further cis-dihydroxylation to yield triols provides a further example of the meta effect during toluene dioxygenase-catalysed oxidations.
利用甲苯双加氧酶（TDO）的来源恶臭假单胞菌UV4，对一系列邻位、间位和对位取代的乙苯和丙苯底物进行了生物转化。邻位和对位取代的烷基苯底物仅产生具有相同绝对构型的相应对映体纯顺式二氢二醇。然而，间位异构体通常除了产生顺式二氢二醇外（间位效应），还生成苄醇生物产物。苄醇具有相同的（R）绝对构型，但对映体过量值各不相同。顺式二氢二醇相似的（2R）绝对构型与乙基和丙基对其他取代基具有主导立体定向作用是一致的。之前用于预测源自取代苯底物的顺式二氢二醇生物产物的区域化学和立体化学的模型已得到改进，以考虑像乙基或丙基这样的不对称取代基。由间位取代的苯底物形成苄基羟基化产物，而没有进一步顺式二羟基化生成三醇，这为甲苯双加氧酶催化氧化过程中的间位效应提供了另一个例子。
