منابع مشابه
On the mechanism of enzymatic cyclization of squalene.
The demonstration that lanosterol is formed from acetate (1) and is converted to cholesterol (2,3) has provided strong support for the hypothesis that lanosterol is an early intermediate in the conversion of squalene to cholesterol (4, 5). The cyclieation of squalene not only to lanosterol, but also to the various cyclic triterpenes, has, in fact, been postulated to proceed in a concerted manne...
متن کاملMechanism of squalene cyclization. The biosynthesis of fusidic acid.
It is generally accepted that the C-20 cation or its stabilized equivalent is an intermediate in the biosynthesis of certain triterpenes and sterols. To evaluate this hypothesis the biosynthesis of the protosterol fusidic acid was investigated. Fusidic acid was biosynthesized by incubating the fungus Fusidium coccineum on a medium containing (3RS,4R)(2-14C,4-3H)-meva10nic acid (MVA). The obtain...
متن کاملCyclization cascade of the C33-bisnorheptaprenoid catalyzed by recombinant squalene cyclase.
The enzymatic cyclization reaction of polyprenoid C(33) by squalene-hopene cyclase (SHC) was investigated with the intention of creating an unnatural hexacyclic compound. The enzymatic products consisted of mono-, bi-, tri-, tetra- and pentacyclic skeletons; however, hexacyclic products were not generated, contrary to our expectations. The absence of a hexacyclic skeleton indicated that the ent...
متن کاملStructural diversity of the triterpenic hydrocarbons from the bacterium Zymomonas mobilis: the signature of defective squalene cyclization by the squalene/hopene cyclase.
Twelve polycyclic triterpenic hydrocarbons (alpha- and gamma-polypodatetraenes, dammara-20(21),24-diene, 17-isodammara-12,24-diene, eupha-7,24-diene, hop-17(21)-ene, neohop-13(18)-ene, 17-isodammara-20(21),24-diene, neohop-12-ene, fern-8-ene, diploptene and hop-21-ene) were detected in the hydrocarbon fraction from the bacterium Zymomonas mobilis. Some of them have never been reported from bact...
متن کاملThe Cyclization of Natural Rubber
The effects of solvent, temperature, time, weight percent of catalyst on the rate and mechanism of cyclization of natural rubber (NR) was studied in toluene and xylene solutions having tin tetra chloride catalyst (SnCl4). Iodometric titration show, with 8% SnCl4 (based on polymer weight) cyclization occurs, leaving 27.4% of the total unsaturation. Infrared spectra of c...
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ژورنال
عنوان ژورنال: Journal of Japan Oil Chemists' Society
سال: 1968
ISSN: 1884-2003
DOI: 10.5650/jos1956.17.543