Aqueous reactions nucleosides

As shovm in Eq 6 59, Rapoport has prepared sinefungin, nucleoside andbiodcs, via nitro-aldol reaction, dehydradon, and reducdon v/iihZn in acetic acid fi-Niiro styrenes are selecdvity reduced to the corresponding oximes by indium metal in aqueous methanol under neutral conthdons ... 

Steenken, S. (1989). Purine bases, nucleosides and nucleotides aqueous solution redox chemistry and transformation reactions of their radical cations and e" and OH adducts. Chem. Rev. 89, 503-520. 

Addition of a radical to the C6-position of thymine residues in DNA generates the C5-thymine radical 74 (Scheme 8.27). Reaction with molecular oxygen, followed by reduction, yields the hydroperoxide 75. Decomposition of the hydroperoxide ultimately yields the hydantoin nucleobase 78 via the ring-opened derivatives 76 and 77 ti,2 for the decomposition of 75 in aqueous solution is slow, with a 9 h for the tra i-isomer and 20 h for the c -isomer of the nucleoside)... 

Whereas imidazolides of nucleotides react only in organic solvents with phosphates or pyrophosphates to give the corresponding anhydride derivatives in high yield, ATP can also be formed enzymatically in aqueous solution from AMP-Im with inorganic pyrophosphate in the presence of valyl-f-RNA synthetase.[66] A variant of this method is the one-pot reaction of a nucleoside with phosphoryltristriazole and tributylammonium pyrophosphate. 671 An a-methylphosphonyl-/ ,y-diphosphate of a thymidine derivative has been synthesized in a similar way t681... 

Imidazolides of adenylic acid (ImpA) or uridylic acid (ImpU) are polycondensed to oligonucleotides by means of Zn2+ ions. 1673 The resulting phosphordiester bond was found to be of the 2, 5 type. In the reaction of nucleoside 5 -phosphoric acid methyl ester with ImpA in the presence of MgC, 2, 5 -dinucleotides are formed six to nine times more frequently than the corresponding 3, 5 compounds. 63 Polycondensations of ImpA in aqueous solution in the presence of various divalent metal ions lead to short oligo-adenylic acids (pA) (n = 1—5) mainly with 2, 5 -intemucleotide linkages. With Pb2+, for example, the total yield of oligomers was as high as 57%. 1683 1693... 

Product distributions obtained on esterification of nucleosides and nucleotides under basic conditions throw further light on factors affecting selective reactivity. p-Toluenesulfonylation of adenosine 5 -monophosphate in aqueous alkali yielded exclusively (in 54-61% yield) the 2 -p-toluenesulfonate.107 Lack of reaction at HO-3 was attributed either to formation of a phosphoric p-toluenesulfonic anhydride, which sterically protected this hydroxyl group, or to the higher acidity of HO-2. It has been shown that the acidic site (with pKa 12.5) in adenosine is associated with the presence of both HO-2 and HO-3, as replacement of either of these by hydrogen, or of HO-2 by methoxyl, results in loss of this acidity.108 Inductive effects, or the sta-... 

TBA)3-HP207 (0.68 g, 0.75 mmol) is added to the nucleoside tosylate (0.5 mmol) in MeCN (0.5 ml) and the solution is stirred at room temperature until the reaction is complete (monitored by NMR spectroscopy). H20 (l ml) is added and the solution is filtered through a 0.45-[xm Millex filter. The filtrate is purified by linear gradient elution from DEAE Fractogel (eluent 0.05-0.5 M aqueous NH4HC03) and the desired fractions are dried by lyophilization. 

Ultraviolet (UV) spectroscopy does not tend to be the method of choice for structure determination, but a list of UV absorptions was given in the review by Knowles <1996CHEC-II(7)489>. Fluorescence properties and triplet yields of [l,2,3]triazolo[4,5-r/ pyridazines in various solvents have been reported <2002JPH83>. These heterocyclic systems were found to be photochemically very stable. In a recent paper, Wierzchowski et al. studied the fluorescence emission properties of 8-azaxanthine ([l,2,3]triazolo[4,5-r/ pyrimidine-5,7-dione) and its A -alkyl derivatives at various pH s <2006JPH276>. For the 8-azaxanthines, an important characteristic of emission spectra in aqueous solutions was the unusually large Stokes shift. Since 8-azaxanthine is a substrate for purine nucleoside phosphorylase II from Escherichia coli, the reaction is now monitored fluorimetrically. The fluorescence properties of [l,2,3]triazolo[4,5-r/ -pyrimidine ribonucleosides were earlier described by Seela et al. <2005HCA751>. 

The favored formation of a nucleoside 3 -(alkyl phosphate) was observed on treating the diphenyl phosphate anhydride of uridine 2, 3 -cyclic phosphate with benzyl alcohol.273 In a somewhat related reaction, on treatment with dicyclohexylcarbodiimide in aqueous pyridine, adenosine 2 (3 )-phosphate gave, initially, the 2, 3 -cyclic phosphate, which, on further reaction with the diimide, gave a mixture of the N-phosphonourea nucleoside 44 and its 2 -isomer, in unequal amounts.269 This type of reaction does not seem to occur with... 

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