Squalenes oxido

The stereoisomeric mixture of -hydroxyalkyl selenides resulting from the reaction of the a-selenoalkyllithium and the carbonyl compound has been often cleanly and easily separated into its constituents by liquid chromatography on silica gel (Schemes 124,133,134, and 170 172).200.206.222,226,229,258 59 jj,jg has, therefore, allowed the synthesis of each of the two stereoisomers of various di- and tri-substituted alkenes (Schemes 124,170 and 171 Scheme 172, a) and epoxides (Scheme 124 Scheme 172, b), which are otherwise obtained as intractable mixtures of stereoisomers through the conventional phosphorus or sulfur ylide methods. Last but not least, 2-lithio-2-methylselenopropane can be used as the precursor of various compounds bearing gem dimethyl substituted carbons, such as squalene, oxido-squalene, lanosterol and cholesterol. Use of commercially available perdeuterated or Ci or — 2 acetone allows the straightforward synthesis of the corresponding labelled compounds... 

Cyclization of Squalene.—Marked differences have been found between specir mens of the enzyme 2,3-oxidosqualene cyclase isolated from yeast and hog liver. In the former organism the enzyme was in the soluble fraction, whereas in the latter it was associated with the microsomes. Further studies of unnatural precursors showed that a preformed steroidal ring-D (65) gave in low yield the corresponding lanosterol analogue (68). Similarly, 6-demethyl-2,3-oxido-squalene (66) was efficiently used and gave 19-norlanosterol (69). ... 

Full details have appeared on the cyclization of squalene (but not 2,3-oxido-squalene) to fem-9(ll)-ene in Polypodium vulgare, and of the incorporation ... 

Abe, I, U. Sai awa, and Y. Ebizuka, Purification of 2,3-oxido-squalene 3-amyrin cyclase from pea seedlings, Chem. Pharm. Bull., 37, 536-538 (1989a). 

Squalene monooxygenase (2,3-epoxydizing) 2 2,3-oxidosqualene cyclase (e.g., 2,3-oxido-squalene lanosterol cyclase and 2,3-oxidosqualene cycloartenol cyclase)... 

E. J. Corey, W. E. Russey, and P. R. Ortiz de Montellano (1966), 2,3-Oxido-squalene, an intermediate in the biological synthesis of sterols from squalene. J. Amer. Chem. Soc. 88, 4750-4751. 

Table I. Properties of Purified (Oxido)Squalene Cyclase Enzymes...

In order to overcome this deficiency in biochemical nomenclature, we suggest that naturalo-(nat) sterols formed biosynthetically from the cyclization of 3(S)-oxido-squalene may be distinguished from unnatural synthetically or abiotically produced sterols (e.g., enantio-(ent)-lanosterol or ent-cholesterol) by examining their 3-... 

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