Vitamin compounds related

Firefly lucifenn is an example of an azole that contains a benzene ring fused to the five membered ring Such structures are fairly common Another example is benzimidazole present as a structural unit m vitamin B12 Some compounds related to benzimidazole include purine and its ammo substituted derivative adenine one of the so called het erocychc bases found m DNA and RNA (Chapter 28)... 

FIGURE 10.2 Structural formula of vitamin and related compounds. 1 — pyridoxine, 2 — pyridoxal, 3 — pyridoxamine, 4 — 4-pyridoxic acid 5 — pyridoxal-5 -phosphate. 

Knoevenagel condensation of diethyl malonate or related compounds with a,fi-unsaturated aldehydes and ketones results in diene esters (equation 40)78. This condensation reaction has been used to extend the polyene chain length of vitamin A related compounds (equations 4179 and 4280). 

Our data suggested that foods with active polyphenolic flavonoids were more resistant than foods with vitamins and related compounds. 

This class includes both vitamin A and the provitamin A carotenoids. All the compounds related to all-trani-retinol (Figure 19.11) are known as vitamin A. These compounds, together with their metabolites and synthetic derivatives, exhibiting the same properties are called retinoids. Vitamin A is found in animal products as retinyl esters (mainly palmitate). 

Parathyroid Hormone, Calcitonin, Vitamin D, and Other Compounds Related to Mineral Metabolism... 

As catalytic semihydrogenation of alkynes to Cis-alkenes is not only a very important synthetic operation (ref. 1) but also of industrial interest, it is a challenging task for both synthetic and catalytic chemists. For instance, the importance of the problem is illustrated by numerous recent publications on different aspects of the selective hydrogenation of many compounds related to the propargyl alcohol structure (refs. 2-7). In this respect, 1,4-butenediol, obtained by the liquid-phase semihydrogenation of 1,4-butynediol, is a raw material for insecticides and Vitamin Bg (refs. 2,8,9). Furthermore, the total and selective liquid-phase hydrogenation of this compound is one of the procedure for making butanediol, the top 95 chemical produced in the United States (refs. 10,11), whose major use is in the manufacture of polyesters. 

Further studies have extended this promotion of auxin and gibberellin action to other fat-soluble substances, in particular some isoprenoid vitamins and related compounds (I). For instance, vitamin E, vitamin Kl9 and phytol are quite comparable in their growth-promoting ability to the fatty acid ester, methyl linoleate. But some fat-soluble vitamins are not active—for instance, vitamin A, -carotene, and vitamin D2. 

Vitamin D is a precursor for a number of compounds that increase intestinal absorption and decrease renal excretion of calcium and phosphate. Metabolites of vitamin D and their pharmacologic analogs are typically used to increase blood calcium and phosphate levels and to enhance bone mineralization in conditions such as osteodystrophy, rickets, or other situations where people lack adequate amounts of vitamin D. Vitamin D analogs such as calcitriol have also been combined with calcium supplements to help treat postmenopausal osteoporosis,4,9 and to treat bone loss caused by antiinflammatory steroids (glucocorticoids see Chapter 29 28.76 Specific vitamin D-related compounds and their clinical applications are listed in Table 31-5. 

Al. Anonymous, Nomenclature policy Generic descriptors and trivial names for vitamins and related compounds. /. Nutr. 106, 8-14 (1976). 

The main dietary precursors of vitamin A-type compounds are the carotenes, chiefly /3-carotene. Compounds derived from this isoprenoid substance (Table 6.2) are involved in the visual process, maintenance of epithelial cell integrity, and even protection against neoplasms. Vitamin A-related compounds may be toxic if ingested in excessive amounts. 

Retinoids (e.g. retinoic acid) are involved in development and in metabolic regulation (e.g. through induction of expression of PEPCK, the rate limiting enzyme in gluconeogenesis). Retinoic acid derives from retinol, which in turn derives from ingestion of plant a-, 3- and "/-carotenes and other carotenes. Retinoic acid acts via retinoic acid receptors and retinoid X receptors note that these receptors can heterodimerize in the nucleus with other related hormone receptors such as PPA-Rs. The developmental importance of retinoic acid is underscored by the teratogenicity of retinoic acid and other vitamin A related compounds, notably some compounds developed for anti-acne properties. 

Although diastereoselective intramolecular al-koxypalladations have been investigated intensively and have found application in synthesis (see above), there are few examples of enantioselective alkoxypalladations [2bJ. For instance, Hosokawa et al. were able to cyclize unsaturated phenol derivatives of type 62 in the presence of chiral (// -allyl-PdOAc complexes, i.e. 63), but only with modest enantioselectivities. Under the same conditions the conversion of the phenol 65 to chroman 66 (a compound related to vitamin E) proceeded in acceptable yields, but with only low asymmetric induction. Newer results by Uozumi et al., for instance the Pd-catalyzed cyclization of 67 to 68 in the presence of a chiral bis-oxazolin ligand [15], show that much higher enantioselectivities can be achieved, at least for certain substrates. 

The results in Figure 9.51 demonstrate that the major vitamin D-related compound in skin not exposed (0 minutes) to ultraviolet (UV) light was 7-dehydro-... 

The benefit of using thin-layer chromatography (TLC) for the identification of unknown vitamins and related compounds by comparing Rf values of the unknown compounds with authentic vitamins is beyond doubt. The quantification of the separated vitamins can be performed by the use of modem densitometry. TLC [or high-performance thin-layer chromatography (HPTLC)], as a powerful separation and analytic tool, is used particularly with pharmaceutical preparations and food products. Because amounts of most hydrophilic vitamins are low, or very low, in tissues or body fluids, bioautography or de-rivatization is used before densitometry. 

Shantz, E. Synthesis of Compounds Related to Vitamin A from Hydroxy-... 

Vs as a lUhydraHng agttU. In the coiirHC of the synlhcHiii of compounds related to vitamin A, Oroahnlk explored the dehydration of the unaaturated corbinol-ether... 

Edenharder, E. et al., Antimutagenic effects and possible mechanisms of action of vitamins and related compounds against genotoxic heterocyclic amines from cooked food, Mutat. Res., 444, 235, 1999. 

L Fotsing, B Boulanger, P Chiap, M Fillet, P Hubert, J Crommen. Multivariate optimization approach for the separation of water-soluble vitamins and related compounds by capillary electrophoresis. Biomed Chromatogr 14 10-11, 2000. 

Retinoids, a group of compounds related to vitamin A which have profound effects on DNA transcription, have an inhibitory effect on cellular proliferation and have been implicated in cellular differentiation (35-37). It has been suggested that depletion of retinoic acid (RA) secondary to retinal detachment may result in morphologic and proliferative changes in RPE that ultimately lead to PVR (38). RA also markedly... 

Interest in these reactions has continued until today because the course and the stereochemistry of many chemical reactions could now be explained and predicted by simple theoretical concepts based on the properties and interactions of the molecular orbitals involved. Pericyclic reactions have found wide application in synthesis, including that of natural products5. Pericyclic reactions involving sigmatropic hydrogen shifts are also observed in biological systems in nature the photochemical and thermal interconversions of compounds related to the vitamin D complex constitute important examples6-8. 

In order to study the nature of activated hydrogens in compounds related to thiamine (vitamin Bj), Hafferl, Lundin, and Ingraham273... 

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