Dihydro vitamin

The hydrogenation of ketones with O or N functions in the a- or / -position is accomplished by several rhodium compounds [46 a, b, e, g, i, j, m, 56], Many of these examples have been applied in the synthesis of biologically active chiral products [59]. One of the first examples was the asymmetric synthesis of pantothenic acid, a member of the B complex vitamins and an important constituent of coenzyme A. Ojima et al. first described this synthesis in 1978, the most significant step being the enantioselective reduction of a cyclic a-keto ester, dihydro-4,4-dimethyl-2,3-furandione, to D-(-)-pantoyl lactone. A rhodium complex derived from [RhCl(COD)]2 and the chiral pyrrolidino diphosphine, (2S,4S)-N-tert-butoxy-carbonyl-4-diphenylphosphino-2-diphenylphosphinomethyl-pyrrolidine ((S, S) -... 

Among ketoesters, tremendous efforts have been devoted to the hydrogenation of dihydro-4,4-dimethyl-2,3-furandione (KPL), not only as a model reaction but also because the product R(-)-pantolactone is a key intermediate in the synthesis of vitamin B5 and coenzyme A (Scheme 33.1). 

Menadione (vitamin K-3, 79) in ethanol in the presence of oxygen was placed in the sun for 10 min to give the 2,3-epoxide (80) [64]. This has been photolysed in micellar solutions to give two main products 2-hydroxy-3-methylnaphtho-quinone and 2,3-dihydro-2-hydroxy-2-methylnaphthoquinone [65]. Solid menadione left on a south-facing windowsill (in Texas ) for a month gave two photodimers the syn head-to-head and syn head-to-tail cyclobutanes. With UV... 

Thiamin (vitamin B-l, 177) when photolysed, gives preparations having a characteristic odour. Photolysis of an aqueous solution with a high-pressure mercury lamp is reported to give the pyrimidine (178) [ 113]. Other work used irradiation at 254 nm and concentrated on the approximately 0.1% yield of ether-soluble odoriferous products. As many as nine compounds have been identified (179), (180), (181), 2-methyl-3-formyl-4,5-dihydrofuran, 3-acetyl-4,5-dihydrofuran, 4-oxopentyl formate, 3-formyl-5-hydroxypentan-2-one, 3-mercapto-2-methyl-4,5-dihydrofuran and bis(4,5-dihydro-2-methylfuran-3-yl)disulphide [114, 115]. 

I. 1.4.1] catalyzes the reaction of 2-methyl-3-phytyl-l,4-naphthoquinone with oxidized dithiothreitol and water to produce 2,3-epoxy-2,3-dihydro-2-methyl-3-phytyl-l,4-naphthoquinone and 1,4-dithiothreitol. In the reverse reaction, vitamin K 2,3-epoxide is reduced to vitamin K and possibly to vitamin K hydroquinone by 1,4-dithioer-ythritol (which is oxidized to the disulfide). Some other dithiols and butane-4-thiol can also act as substrates. This enzyme is strongly inhibited by warfarin. 

K. Ando, F. Kondo, F. Koike, H. Takayama, Synthesis of 24,24-difluoro-la-dihydro-vitamin D3 from vitamin D2, Chem. Pharm. Bull. 40 (1992) 1662-1664. 

Ionone is converted into intermediates for vitamin A synthesis. The hydrogenation of ionones and methylionones is of some importance. Dihydro or tetrahydro derivatives or ionols can be obtained depending on reaction conditions. 

Folate is a relatively unstable nutrient processing and storage conditions that promote oxidation are of particular concern since some of the forms of folate found in foods are easily oxidized. The reduced forms of folate (dihydro- and tetrahydrofolate) are oxidized to p-aminobenzoylglutamic acid and pterin-6-carboxylic acid, with a concomitant loss in vitamin activity. 5-Methyl-H4 folate can also be oxidized. Antioxidants (particularly ascorbic acid in the context of milk) can protect folate against destruction. The rate of the oxidative degradation of folate in foods depends on the derivative present and the food itself, particularly its pH, buffering capacity and concentration of catalytic trace elements and antioxidants. 

Two derivatives of nicotinamide (pyridine-3-carboxylic amide), one of the B2 vitamins, nicotinamide adenine dinucleotide (NAD ) and nicotinamide adenine dinucleotide phosphate (NADP ), serve as redox coenzymes. Of the three heterocyclic ring systems found in these coenzymes, i.e. those of purine, ribose and pyridine, it is the pyridine portion that is reactive in redox reactions. Biologically, two oxidation states are important the oxidized form, NAD(P)+, and the 1,4-dihydro isomer of the two-electron reduced form, NAD(P)H (Scheme 1). Nicotinamide coenzymes interconvert between these two oxidation states in... 

Although alkylbenzofuran derivatives (e.g., 2-methyl-2,3-dihydro-benzofuran) have no vitamin F activity,88 they seem to show some regulating activity on plant growth.89 The 2,2-dimethyl-2,3-dihydro-benzofuran ring is an effective toxophore.90... 

Dioxepane 55 has found application in the manufacturing of vitamin B6. Cycloadduct 55 was obtained by Diels-Alder reaction of 2-isopropyl-4,7-dihydro-l,3-dioxepin with 4-methyl-5-ethyloxy-l,3-oxazol (see Section 13.11.6.2), and the resulting adduct was rearranged in the presence of an acid to give pyridoxol derivative 268 <2004DE10261271A1, 2005W0049618A1> (Scheme 83). 

Synthetic dihydro form (KH2) coenzyme for "y-carboxyglutamic acid formation on procagulant factors II, VII, IX, X, anticoagulant proteins C S, matrix Gla protein osteocalcin Synthetic cf. Dicoumarol, Vitamins K,K2 K3... 

SYNS ADENINLMINE 6-AMINOPURINE 6-A.MINO-IH-PURINE 6-AMINO-3H-PURINE 6-AMINO-9H-PURINE 1.6-DIHYDRO-6-IMINO-PURINE 3,6-DIHYDRO-6-IMINOPURINE LEUCO-4 IH-PURIN-6-AMINE USAF CB-18 VITAMIN B4... 

BF3 Et20 is useful for the condensation of allylic alcohols with enols. A classic example is the reaction of phytol in dioxane with 2-methyl-l,4-naphthohydroquinone 1-monoacetate to form the dihydro monoacetate of vitamin Ki (Eq. 30), which can be easily oxidized to the quinone [57]. 

A cofartor can be any chemical required by an enzyme, that is, a metal ion, coenzyme, lipid, or accessory pmtein. A coenzyme is a small organic molecule required by an enzyme that participates in the chemistry of catalysis. Most of the coenzymes work according to the following principle. They shuttle back and forth between two or more different forms. I lere, one of the forms may be considered to be the coenzymatically active form, and the other may be seen as requiring regeneration to the active form. This is the case for folate, vitamin B, riboflavin-and niacin-based cofactors, ascorbic acid, and vitamin K. The coenzymatically active (inactive) forms of three of these coenzymes are tetrahydrofolate (dihydro-folate), ascorbic acid (dehydroascorbic acid), and vitamin KH2 (vitamin K). 

Prieme, H., Loft, S., Nyyssonen, K., Salonen, J. T., and Poulsen, H. E. (1997). No effect of supplementation with vitamin E, ascorbic acid, or coenzyme QIO on oxidative DNA damage estimated by 8-oxy-7,8-dihydro-2-deoxyguanosine excretion in smokers. Am.. Clin. Nutr. 65, 503-507. 

The method was applied to the solubility of tioconazole and 19-Nor-la,25-dihydro vitamin D2 in several ternary and in a quaternary aqueous mixed solvents. The predicted solubilities were compared with experimental data and good agreement was found. 

Synonyms ( )-3,4-dihydro-2,5,7,8-tetramethyl-2-(4,8,12-tri-methyltridecyl)-2H-l-benzopyran-6-ol acetate ( )-(2R5,4 R5,8 R5)-2,5,7,8-tetramethyl-2-(4, 8, 12 -trimethyl-tridecyl)-6-chromanyl acetate ( )-a-tocopherol acetate a-tocopheroli acetas alTrac-a-tocopheryl acetate dl-a-toco-pheryl acetate vitamin E. 

Synonyms cumotocopherol ( )-3,4-dihydro-2,5,8-trimethyl-2-(4,8,12-trimethyltridecyl)-2H-l-P-benzopyran-6-ol 5,8-dimethyltocol neotocopherol d/-P-tocopherol vitamin E p-xylotocopherol. 

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