72633-85-3Relevant academic research and scientific papers
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
Hoshino, Tsutomu,Kondo, Tomohiro
, p. 731 - 732 (1999)
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.
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
Kaneko, Ikki,Terasawa, Yuri,Hoshino, Tsutomu
, p. 11139 - 11157 (2018/08/03)
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 products; however, the analog possessing the Et group at the 23Z position (23Z-Et-1) gave two hopene homologs and the neohopane skeleton, but no hopanol homologs. Hopene homolog (C31) was generated from 23E-Et-1 by deprotonation from 23Z-Me (normal cyclization cascade). Intriguingly, the same homolog was also generated from the geometrical isomer 23Z-Et-1, indicating C?C bond rotation about the C-21?C-22 axis of the hopanyl cation and the more compact nature of the binding domain at 23Z compared with 23E. On the other hand, analogs with the CH2OH group gave novel hopane skeletons having 1-formylethyl and 1-hydroxyprop-2-en-2-yl residues at C-21. Products bearing an aldehyde group were generated in higher yield from 23Z-CH2OH-1 (89 %), than from 23E-CH2OH-1 (26 %). The significant yield (26 %) of the aldehyde products from 23E-CH2OH-1 indicated that C?C bond rotation had occurred owing to the absence of hydrophobic interactions between the hydrophilic 23E-CH2OH and its binding site. The polycyclization mechanisms of the four different analogs are discussed.
