Cytosine reaction with

The analogons deamination reaction is not observed in l-methyl-2 -deoxy-adenosine nncleosides. ° Rather, in the adenine series, the Dimroth rearrangement occnrs (Scheme 8.4). On the contrary, in styrene adducts of 2 -deoxyadenosine, the hydroxyl residue of the adduct undergoes intramolecular reaction with the base to initiate deamination (Scheme 8.6). ° ° Similarly, cytosine residues bearing styrene adducts at the N3-position undergo rapid deamination (nearly complete deamination is seen within 75h). °°... 

DNA and RNA may be modified with hydrazide-reactive probes by reacting their cytosine residues with bisulfite to form reactive sulfone intermediates. These derivatives can undergo transamination reactions with hydrazide- or amine-containing probes to yield covalent bonds (Draper and Gold, 1980) (Chapter 27, Section 2.1). 

Figure 27.2 Treatment of cytosine bases with bisulfite results in a multi-step deamination reaction, ultimately leading to uracil formation.

The synthesis of the pyrimidines involves cyanoacetylene, which is synthesised in good yield from discharge reactions of CH4 and N2. The reaction with cyanoacetylene or cyanoacetylaldehyde, in a concentrating environment, produces cytosine and uracil according to Figure 8.6. 

Sulfoxides have also been used in the synthesis of nucleoside analogs (Scheme 3.2). Chanteloup and Beau reported the synthesis of ribofuranosyl sulfoxide 13 and its use in the glycosylation of a series of silylated pyrimidine and purine bases.7 Although 16 is not an anomeric sulfoxide, its reaction with cytosine derivative 17 is conceptually related.8... 

Cytosine can become deaminated spontaneously or by reaction with nitrous acid to form uracil. This leaves an improper base pair (G-U), which is eliminated by a base excision repair mechanism (Figure 1-2-5). Failure to repair the improper base pair can convert a normal G-C pair to an A-T pair. 

The pyrimidines cytosine and thymine both react with hydrazine, which initially attacks the unsaturated carbonyl system and then leads to ring opening. Again, base treatment is used to hydrolyse the phosphodiester bond. This reaction becomes selective for cytosine in the presence of NaCl, which suppresses reaction with thymine. 

Murata T, Saito G (2006) Properties of reaction products between cytosine and F4TCNQ in MeOH two hemiprotonated cytosine salts with F4TCNQ radical anion and methoxy adduct anion. Chem Lett 35 1342-1343... 

One of the powerful chemical mutagens inducing point mutations is hydroxylamine, NH2OH, and its N- and O-methyl derivatives.125-133 These react with the pyrimidine bases, and their reaction with cytosine (or cytidine) leads to the formation of several modified cytosines (or cytidines), among which are lV4-hydroxycytosine (21, 22, R = R = H), and A4-methoxycytosine (21, 22, R = H, R = Me) and the... 

Schuchmann MN, Naumov S, Schuchmann H-P, von Sonntag J, von Sonntag C (2005) 4-Amino-3Ff-pyrimidin-2-one ("isocytosine") is a short-lived non-radical intermediate formed in the pulse radiolysis of cytosine in aqueous solution. Radiat Phys Chem 72 243-250 Schulte-Frohlinde D, Hildenbrand K (1989) Electron spin resonance studies of the reactions of OH and SO4 radicals with DNA, polynucleotides and single base model compounds. In Minisci F (ed) Free radicals in synthesis and biology. Kluwer, Dordrecht, pp 335-359 Schulte-Frohlinde D, Behrens G, Onal A (1986) Lifetime of peroxyl radicals of poly(U), poly(A) and single- and double-stranded DNA and the rate of their reaction with thiols. Int J Radiat Biol 50 103-110... 

Several other proteins show a low, but significant amino acid identity with atzA (Table 22.4). All of these, urease-alpha subunit (urea amidohydrolase), cytosine deaminase, and imidazolone-5-propionate hydrolase, catalyze hydrolytic reactions with substrates involved in the metabolism of nitrogenous compounds (Sadowsky et al 1998). A Rhizobium strain capable of atrazine dechlorination has been isolated from a soil that was previously treated with atrazine (Bouqard et al., 1997). This bacterium could not mineralize atrazine, and it accumulated hydroxyatrazine as the sole metabolite after long-term incubations. Interestingly, 22 of the 24 identified amino acids at the N-terminus of the atrazine halidohydrolase from Rhizobium were identical with atzA from Pseudomonas strain ADP. 

Table VII summarizes additional examples of allylations of 190 and 191 as well as of cytosine 200 and 5-methylcytosine 201 (Scheme 44) with electrophiles 74, rac-166, and rac-204 together with the targeted final products. Reactions with glycoside 74 and with vinyl epoxide 204 always occur with overall retention of configuration. The reactions with cyclopentene derivatives are related to the preparation of synthetic carbanucleosides with antiviral action.

The reaction of 4-aminopyrimidines with hexafluoroacetone in DMF gives pyrimido[4,5-d][l,3]oxazines e.g. treating cytosine (196) with hexaflouroacetone gave 5,7-di-(di-(trifluoro-methyl))-(li/,3//)-pyrimido[4,5- ][l,3]oxazin-2-one (197) (Equation (29)) (87IZV1433,89izvi656>. 

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