Cyclization of Polyenes. III Cyclization of Squalene-oxides
نویسندگان
چکیده
منابع مشابه
Asymmetric oxidative cation/olefin cyclization of polyenes: evidence for reversible cascade cyclization.
The biosynthesis of cyclic terpenes from polyene precursors by cyclase enzymes is one of nature’s most elegant chemical transformations.[1] The ease with which nature creates complex molecular architectures from achiral precursors has motivated efforts to develop similarly powerful synthetic methodologies.[2] Alimited number of asymmetric methods have been developed,[3] including the notable Br...
متن کاملEnantioselective Cascade Cyclization/Protodemetalation of Polyenes with N3Pt2+ Catalysts
The combination of the N-based pincer ligand PyBOX with Pt2+ leads to new catalysts for the enantioselective cycloisomerization of dienyl- and trienyl-ols. The mechanistic combination of electrophilic cyclization followed by rapid protodemetalation is surprising and leads to a powerful construct for developing new reactions.
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 کاملOn 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 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: Chemical and Pharmaceutical Bulletin
سال: 1968
ISSN: 0009-2363,1347-5223
DOI: 10.1248/cpb.16.2216