The cyclization mechanism of squalene in hopene biosynthesis: the terminal methyl groups are critical to the correct folding of this substrate both for the formation of the five-membered E-ring and for the initiation of the polycyclization reaction†
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
The cyclization mechanism of squalene in hopene biosynthesis: the terminal methyl groups are critical to the correct folding of this substrate both for the formation of the five-membered E-ring and for the initiation of the polycyclization reaction†
作者:Tsutomu Hoshino
DOI:10.1039/a901351b
日期:——
Incubations of C(23)-norsqualenes 5 and 6, lacking one of the two terminal methyl groups, with squalene-hopene cyclase gave unprecedented products 7 and 8 having a tetrahymanol skeleton together with a neohopane skeleton 12, strongly suggesting that the two geminal methyls of squalene 1 are critical to the formation of the five-membered E-ring in hopene biosynthesis and also are required to initiate the cyclization reactions of 1 into the pentacyclic triterpenes 2 and 3.