Synthesis of Ara

The reaction temperature is very important and a key to the synthesis of ara-A. As shown in Fig. 2, by-product hypoxantine is formed from substrate adenine by the reaction of the adenine deaminase of microorganisms in a temperature range of 30 C-50 C, then, ara-A is not formed under these conditions. 

One such factor that is in human milk, but not in conventional infant formula, is arachidonic acid (ARA 20 4n-6) (Table 1). In human milk from Western populations, ARA is usually 0.5% of total fatty acids, but on a world-wide basis, its concentration ranges from 0.1 to 0.7% of total fatty acids (3). Dietary ARA could promote tissue accumulation of this essential fatty acid and subsequent synthesis of ARA-de-rived eicosanoids in the mucosa. 

Fig. 16 Yakura s iodane-catalyzed synthesis of /)ara-quinols and Hamed s asymmetric version...

Nachman, R.J., Wong, R.Y, Haddon, W.F., and Lundin, R.E. (1985) Synthesis of ara-doridosine, a new arabinosyl nudeoside resistant to adenosine deaminase. X-ray structure determination of methylisoguanine./. Chem. Soc. Perkin Trans. 1,1315-1321. 

Scheme 3b). It is instructive at this point to reiterate that the furan nucleus can be used in synthesis as a progenitor for a 1,4-dicarbonyl. Whereas the action of aqueous acid on a furan is known to provide direct access to a 1,4-dicarbonyl compound, exposure of a furan to an alcohol and an acid catalyst should result in the formation of a 1,4-diketal. Indeed, when a solution of intermediate 15 in benzene is treated with excess ethylene glycol, a catalytic amount of / ara-toluenesulfonic acid, and a trace of hydroquinone at reflux, bisethylene ketal 14 is formed in a yield of 71 %. The azeotropic removal of water provides a driving force for the ketalization reaction, and the presence of a trace of hydroquinone suppresses the formation of polymeric material. Through a Finkelstein reaction,14 the action of sodium iodide on primary bromide 14 results in the formation of primary iodide 23, a substance which is then treated, in crude form, with triphenylphosphine to give crystalline phosphonium iodide 24 in a yield of 93 % from 14.

Poly(phenylenethylene), dendronized, 522 Poly(phenylenevinylene) optically active, 510-511 synthesis of, 495-496 Poly(/ ara-phenylenevinylene)s, 472 Polypheny lquinoxaline (PPQ) hyperbranched, 312-314 synthesis of, 309-313 Polyphosphoric acid, 333 Polypropylene oxide) polyol, 223 Polypropylene polyols, 220 Poly (pyridine), synthesis of, 503-505 Polyquinoxaline (PQ), synthesis of, 309-313... 

Sasai, H., Arae, S., Tahara, Y., and Shibasaki, M., Catalytic asymmetric synthesis of alpha-amino phosphonates using lanthanoid-potassium-BINOL complexes, /. Org. Chem., 60, 6656, 1995. 

The key transformation in the synthesis of carbanucleosides, reported by Horvath, was based on the Ferrier-II rearrangement and led to the important derivative ara-cyclohexenyl-A (Fig. 19).32... 

For design of a simple manufacturing process, the thermostability of the NP enzymes is a very useful feature. Although heat treatment can be used as part of a purification protocol to isolate the enzymes from contaminating materials, the high temperature of operation itself excludes undesired enzyme-catalysed side reactions. For example, in the synthesis of 9-p-D-arabinofuranosyladenine from Ara-U and adenine, using a wet cell paste of Enterobacter aerogenes, adenine and Ara-U mainly underwent deamination at lower temperatures to form hypoxanthine and uracil respectively. At elevated temperature, deamination was completely eliminated and the rate of transarabinosylation increased. 

Regioselective oxidation by brominolysis of dioxastannolane obtained from methyl / -L-ara-binopyranoside made it possible to accomplish (after subsequent oximation and reduction) a facile synthesis of 4-amino-4-deoxy-L-arabinose, an amino-sugar found in lipopolysaccharides of some Salmonella R. mutant strains <83CPB3778>. 

Viral DNA polymerase is an important catalyst for the synthesis of viral nucleic acids. DNA polymerase inhibitors have already been encountered as antitumor agents. Ara-A (9.5, vidarabine) is a DNA polymerase inhibitor that has demonstrated activity against herpes simplex virus type I (HSV-1) infections, responsible for cold sores on... 

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