Squalene-Hopene Cyclase: Mechanistic Insights into the Polycyclization Cascades of Squalene Analogs Bearing Ethyl and Hydroxymethyl Groups at the C-2 and C-23 Positions
作者:Ikki Kaneko、Yuri Terasawa、Tsutomu Hoshino
DOI:10.1002/chem.201801668
日期:2018.8.1
Squalene‐hopene cyclase (SHC) catalyzes the conversion of squalene 1 into 6,6,6,6,5‐fused pentacyclic hopene 2 and hopanol 3. To elucidate the binding sites for the terminal positions of 1, four analogs, having the larger ethyl (Et) and the hydrophilic CH2OH groups at the 23E or 23Z positions of 1, were incubated with SHC. The analog with the Et group at the 23E position (23E‐Et‐1) yielded two tetra‐ and three pentacyclic
角鲨烯-戊环化酶(SHC)催化角鲨烯1转化为6,6,6,6,6-5融合的五环戊二烯2和Hopanol 3。为了阐明的结合位点的末端位置1,四个类似物,具有较大乙基(Et)和亲水性CH 2在23 OH基团ë或23个ż的位置1,用SHC孵育。Et基团位于23 E位置(23 E‐ Et- 1)的类似物产生了两个四环和三个五环产物。但是,在23 Z位置具有Et基团的类似物(23 Z -Et-1)给出了两个希望的同系物和新庚烷骨架,但没有霍帕醇的同系物。通过从23 Z- Me(正常环化级联)去质子化,从23 E- Et- 1生成Hopene同源物(C 31)。有趣的是,几何异构体23 Z ‐Et - 1也产生了相同的同系物,表明环烷阳离子的C-C键绕C-21-C-22轴旋转,并且结合域在23位时具有更紧密的性质Z与23 E相比。另一方面,CH 2的类似物OH基团给出了新颖的hop烷骨架,其在C-21