Toluene Dioxygenase-Catalyzed Synthesis and Reactions of cis-Diol Metabolites Derived from 2- and 3‑Methoxyphenols

Using toluene dioxygenase as biocatalyst, enantiopure cis-dihydrodiol and cis-tetrahydrodiol metabolites, isolated as their ketone tautomers, were obtained from meta and ortho methoxyphenols. Although these isomeric phenol substrates are structurally similar, the major bioproducts from each of these biotransformations were found at different oxidation levels. The relatively stable cyclohexenone cis-diol metabolite from meta methoxyphenol was isolated, while the corresponding metabolite from ortho methoxyphenol was rapidly bioreduced to a cyclohexanone cis-diol. The chemistry of the 3-methoxycyclohexenone cis-diol product was investigated and elimination, aromatization, hydrogenation, regioselective O-exchange, Stork–Danheiser transposition and O-methylation reactions were observed. An offshoot of this technology provided a two-step chemoenzymatic synthesis, from meta methoxyphenol, of a recently reported chiral fungal metabolite; this synthesis also established the previously unassigned absolute configuration.以甲苯双加氧酶（toluene dioxygenase）作为生物催化剂，从间甲氧基苯酚与邻甲氧基苯酚中，分离得到以酮式互变异构体形式存在的对映体纯顺式二氢二醇（enantiopure cis-dihydrodiol）与顺式四氢二醇（cis-tetrahydrodiol）代谢产物。尽管这类异构酚类底物结构相似，但两种生物转化反应的主要产物却呈现出不同的氧化水平：从间甲氧基苯酚生成的稳定性较好的环己烯酮型顺式二醇代谢产物可被分离纯化，而从邻甲氧基苯酚得到的对应代谢产物则会被快速生物还原为环己酮型顺式二醇。研究人员对3-甲氧基环己烯酮顺式二醇产物的化学特性展开了系统探究，观测到了消除反应、芳构化反应、氢化反应、区域选择性氧交换反应、Stork–Danheiser重排反应（Stork–Danheiser transposition）以及O-甲基化反应。该技术的一项衍生应用开发出了一条以间甲氧基苯酚为起始原料的两步化学酶法合成路线，用于合成近期报道的手性真菌代谢产物（chiral fungal metabolite），该合成路线同时确定了此前未被指定的绝对构型（absolute configuration）。