He Xiaofei, Cane David E
Department of Chemistry, Box H, Brown University, Providence, Rhode Island 02912-9108, USA.
J Am Chem Soc. 2004 Mar 10;126(9):2678-9. doi: 10.1021/ja039929k.
Incubation of farnesyl diphosphate (1, FPP) with recombinant germacradienol synthase from Streptomyces coelicolor A3(2) gave, in addition to (4S,7R)-germacra-1(10)E,5E-diene-11-ol (2), 15% of (-)-germacrene D (5). Incubations of [1,1-2H2]FPP (1a), (1R)-[1-2H]FPP (1b), and (1S)-[1-2H]FPP (1c) with germacradienol/germacrene D synthase and analysis of the resulting samples of germacradienol (2) and germacrene D (5) by a combination of 1H, 2H, and 13C NMR and mass spectrometry established that it is H-1si of FPP that is lost in the formation of germacradienol (2) and that undergoes 1,3-hydride transfer in the formation of (-)-germacrene D (5). The proportion of the two products was also sensitive to isotopic labeling, with cyclization of (1S)-[1-2H]FPP (1c) giving an increased proportion (35%) of 5. These results could be explained by a mechanism involving partitioning of a common helminthogermacradienyl cation intermediate 7.
将法尼基二磷酸（1，FPP）与来自天蓝色链霉菌A3(2)的重组牻牛儿二烯醇合酶一起温育，除了得到(4S,7R)-牻牛儿-1(10)E,5E-二烯-11-醇（2）之外，还得到了15%的(-)-牻牛儿烯D（5）。将[1,1-2H2]FPP（1a）、(1R)-[1-2H]FPP（1b）和(1S)-[1-2H]FPP（1c）与牻牛儿二烯醇/牻牛儿烯D合酶一起温育，并通过1H、2H和13C NMR以及质谱联用对所得的牻牛儿二烯醇（2）和牻牛儿烯D（5）样品进行分析，结果表明，在牻牛儿二烯醇（2）的形成过程中失去的是FPP的H-1si，并且在(-)-牻牛儿烯D（5）的形成过程中它会发生1,3-氢化物转移。这两种产物的比例也对同位素标记敏感，(1S)-[1-2H]FPP（1c）的环化使得产物5的比例增加（35%）。这些结果可以用一个涉及共同的蠕孢牻牛儿二烯基阳离子中间体7的分配机制来解释。
