Vitamine E precursor

The heterogeneous catalytic system iron phthalocyanine (7) immobilized on silica and tert-butyl hydroperoxide, TBHP, has been proposed for allylic oxidation reactions (10). This catalytic system has shown good activity in the oxidation of 2,3,6-trimethylphenol for the production of 1,4-trimethylbenzoquinone (yield > 80%), a vitamin E precursor (11), and in the oxidation of alkynes and propargylic alcohols to a,p-acetylenic ketones (yields > 60%) (12). A 43% yield of 2-cyclohexen-l-one was obtained (10) over the p-oxo dimeric form of iron tetrasulfophthalocyanine (7a) immobilized on silica using TBHP as oxidant and CH3CN as solvent however, the catalyst deactivated under reaction conditions. 

FIGURE 2.12. Silyl-Claisen rearrangement leading to a vitamin E precursor... 

Further, a marine antibiotic, (—)-malyngolide, discovered recently in the marine blue alga Lyngbya majuscula Gomont and the vitamin E precursor chromanmetha-nol were synthesized in high e. e. by utilizing this asymmetric reaction (Scheme 6 and 7). 

The hydrogenation of y-tocotrienyl acetate, a vitamin E precursor [43], is a striking example demonstrating the potential of these catalysts. With complex 27 all three double bonds in the side chain were reduced with very high enantio- and diastereoselectivity to give the natural (R,R,R)-isomer of y-tocotrienyl acetate almost exclusively. Complexes... 

Vitamin Soybean [15] Overexpression of enzymes (chorismate mutase-prephenate dehydrogenase, homogentisate phytyltrans-ferase, and p-hydroxyphenylpyruvate dioxygenase) that are involved with the biosynthesis of vitamin E precursors (increase in tocodiromanols, including tocotrienol)... 

Potassium ascorbate vitamin D source, enriched farina Yeast, dried irradiated vitamin D, pharmaceuticals Cod liver oil vitamin deriv., hair care Panthenyl triacetate vitamin deriv., lip care Panthenyl triacetate vitamin deriv., massage oils Panthenyl triacetate vitamin deriv., skin care Panthenyl triacetate vitamin deriv., skin care oils Panthenyl triacetate vitamin E precursor synthesis N-Methyl-2-pyrrolidone vitamin E source Wheat (Triticum vulgare) germ oil vitamin E source, food... 

Uses Solvent, solubilizer for phamtaceulicals chem. reaction medium reaction solvent in many syntheses ind. vitamin E precursor solubilizer for topicals for applic. to human or animal hair, skin bioavailability enhancer for topicals skin penetration enhancer extraction solvent bioadhesive spray bandages Features Nonaq. increases water sol. of chloramphenicol, procaine, other therapeutic compds. increases sol n. stability of drugs in aq. sol n. 

Vitamin E (tocopherol) is the most important antioxidant in the body, acting in the lipid phase of membranes and protecting against the effects of free radicals. Vitamin K functions as cofactor to a carboxylase that acts on glutamate residues of clotting factor precursor proteins to enable them to chelate calcium. 

De Ritter, A.E., Carotenoid analytical methods, in Carotenoids as Colorants and Vitamin A Precursors, Bauemfeind, J.C., Ed., Academic Press, New York, 1981, 815. Krinsky, N.I., The biological properties of carotenoids. Pure Appl. Chem., 66, 1003,1994. 

Addition of such a-lithiosulfinyl carbanions to aldehydes could proceed with asymmetric induction at the newly formed carbinol functionality. One study of this process, including variation of solvent, reaction temperature, base used for deprotonation, structure of aldehyde, and various metal salts additives (e.g., MgBrj, AlMej, ZnClj, Cul), has shown only about 20-25% asymmetric induction (equation 22) . Another study, however, has been much more successful Solladie and Moine obtain the highly diastereocontrolled aldol-type condensation as shown in equation 23, in which dias-tereomer 24 is the only observed product, isolated in 75% yield This intermediate is then transformed stereospecifically via a sulfoxide-assisted intramolecular 8, 2 process into formylchromene 25, which is a valuable chiron precursor to enantiomerically pure a-Tocopherol (Vitamin E, 26). 

Other dietary factors implicated in prostate cancer include retinol, carotenoids, lycopene, and vitamin D consumption.5,6 Retinol, or vitamin A, intake, especially in men older than age 70, is correlated with an increased risk of prostate cancer, whereas intake of its precursor, [3-carotene, has a protective or neutral effect. Lycopene, obtained primarily from tomatoes, decreases the risk of prostate cancer in small cohort studies. The antioxidant vitamin E also may decrease the risk of prostate cancer. Men who developed prostate cancer in one cohort study had lower levels of l,25(OH)2-vitamin D than matched controls, although a prospective study did not support this.2 Clearly, dietary risk factors require further evaluation, but because fat and vitamins are modifiable risk factors, dietary intervention may be promising in prostate cancer prevention. 

New isoxazoline derivatives of a-tocopherol, the main component of vitamin E, have been synthesized in a facile, two-step sequence consisting of nitration followed by 1,3-dipolar cycloaddition. 5-Nitromethyl-a-tocopheryl acetate, obtained from a-tocopheryl acetate by direct nitration in one step, act as the nitrile oxide precursor in the reaction with various alkenes. The facile conversion proceeds in the presence of equimolar amounts of PhNCO and catalytic amounts of triethylamine to give isoxazolines, 446 (489). 

Takaya and co-workers46 found that BINAP-based Ru(II) dicarboxylate complexes 31 can serve as efficient catalyst precursors for enantioselective hydrogenation of geraniol (2E)-32 and nerol (2Z)-32. (R)- or (iS )-citroncllal 33 is obtained in nearly quantitative yield with 96-99% ee. The nonallylic double bonds in geraniol and nerol were intact. Neither double bond migration nor (fi)-/(Z)-isomerization occurred during the catalytic process. Furthermore, the S/C ratio was extremely high, and the catalyst could easily be recovered (Scheme 6-18). This process can be applied to the asymmetric synthesis of a key intermediate for vitamin E. 

Lipids are important components of the diet fatty acids are the higher energetic source as they ensure 9kcal/g. Furthermore, some peculiar fatty acids themselves and several components of the unsaponifiable fraction are biologically active molecules, as they can act as vitamins (tocopherols— vitamin E), provitamins (carotenes—vitamin A, cholecalcipherol—vitamin D), vitamin-like (essential fatty acids), and hormones or hormone precursors (sterols—steroidal hormones). 

Addition of Active C-H Compounds to Dienes the Rhone-Poulenc Process for Geranylacetone - Geranylacetone is a precursor of isophytol, a key intermediate in the manufacture of vitamine E (tocopherol) (see Figure 16), the world market of which is 10 000 t/a at a price of 25-30 /kg tocopherylacetate.54... 

Vitamin A (retinol, 6.1) is the parent of a range of compounds known as retinoids, which possess the biological activity of vitamin A. In general, animal foods provide preformed vitamin A as retinyl esters (e.g. 6.5, which are easily hydrolysed in the gastrointestinal tract) while plant foods provide precursors of vitamin A, i.e. carotenoids. Only carotenoids with a /3-ionone ring (e.g. /1-carotene) can serve as vitamin A precursors. /3-Carotene (6.6)... 

Vitamins are chemically unrelated organic compounds that cannot be synthesized by humans and, therefore, must must be supplied by the diet. Nine vitamins (folic acid, cobalamin, ascorbic acid, pyridoxine, thiamine, niacin, riboflavin, biotin, and pantothenic acid) are classified as water-soluble, whereas four vitamins (vitamins A, D, K, and E) are termed fat-soluble (Figure 28.1). Vitamins are required to perform specific cellular functions, for example, many of the water-soluble vitamins are precursors of coenzymes for the enzymes of intermediary metabolism. In contrast to the water-soluble vitamins, only one fat soluble vitamin (vitamin K) has a coenzyme function. These vitamins are released, absorbed, and transported with the fat of the diet. They are not readily excreted in the urine, and significant quantities are stored in Die liver and adipose tissue. In fact, consumption of vitamins A and D in exoess of the recommended dietary allowances can lead to accumulation of toxic quantities of these compounds. 

Production sites for vitamin E biosynthesis occur in nuts, seeds, cereal germ, green leaves, legumes. Biosynthesis also occurs in some microorganisms. Precursors for biosynthesis include mevalonic acid and phenylalanine (probably these compounds with side chains). Considerably more research is required to pinpoint the exact precursors. Tocotnenol occuis as ail intermediate in the biosynthesis. 

ACE drinks, containing beta-carotene (vitamin A precursor) and vitamins C and E. These materials are antioxidants and there is evidence that eliminating free radicals in the body will protect against cancer and cardiovascular diseases, particularly in older people. Suggested levels to... 

Rather surprisingly, the average person knows the names of several cofactors and coenzyme precursors, because many of these cannot be synthesized in vivo, and must be supplied in one s diet. This is the reason why a balanced diet should include retinol (vitamin A), ascorbic add (vitamin C), tocopherol (vitamin E), thiamine (vitamin Eh), folic acid etc., as well as zinc and iron. 

---