Thymine 1 - conjugate

The two strands of the nucleic acid DNA are held together by four organic bases. The structure of one of these bases, thymine, is shown below, (a) How many protons can this base accept (b) Draw the structure of each conjugate acid that can be formed, (c) Mark with an asterisk any structure that can show amphiprotic behavior in aqueous solution. 

Conjugation via Bromine Activation of Thymine, Guanine, and Cytosine... 

Such dideoxynucleosides as CNT (306) and the potent anti-HIV drug ddC (307) have been obtained (280), respectively, from the butenolide 248 and from its saturated analogue. Thus, conjugate addition of cyanide to 248, followed by reduction of the lactone group, acetylation of HO-1, and coupling with silylated thymine, afforded, after deprotection, compound 306. 

Pyrimidine is a weaker base than pyridine because of the presence of the second nitrogen. Its conjugate acid is a much stronger acid (pATa = 1.0). The pA a values of the N-l hydrogen in uracil, thymine and cytosine are 9.5, 9.8 and 12.1, respectively. Pyrimidine is a hygroscopic solid (b.p. 123-124 °C, m.p. 20-22 °C) and soluble in water. 

The Fc-modified uridine was incorporated into DNA trinucleotides with standard solid-phase synthesis. An interesting Fc conjugate has also been reported recently having an Fc group linked to two nucleobases such as thymine/uracil. These conjugates form supramolecular assemblies by base paring directed self-assembly.92... 

In a different, biological context the photochemical cydo-dimerization of carbonyl-conjugated alkenes is important as a major source of ultraviolet-induced damage to living cells. Thymine (2.77)... 

Nucleobases and nucleosides are common motifs for hydrogen-bonded supramolecular arrays. Ng et al. first reported a series of phthalocyanine-nucleobase conjugates [64], The tetra-adenine phthalocyanine 64 was prepared by standard <9-alkylation of zinc(II) tetrahydroxyphthalocyanine with 9-(2-bromoethyl)adenine in the presence of K2CO3. The fluorescence of 64 is quenched substantially upon addition of thymine-substituted 9,10-anthraquinone 65, and the rate is much faster compared with that for the situation when the unsubstituted 9,10-anthraquinone is used as the quencher. These results suggest that 64 forms a supramolecular complex with 65 through the Watson-Crick base-pairing interactions. 

Thymine and uracil behave similar to typical carbonyl compounds, i.e. the first intermediate is a radical anion [reaction (55)] which is in equilibrium with its oxygen-protonated conjugated acid [reaction (57)]. The other functional groups, especially the second carbonyl function, withdraw electron density, and hence the p a values of these oxygen-protonated radical anions are much lower (thymine p a = 6.9 [52]) than those of the corresponding radicals from simple carbonyl compounds. However, the C(6)-protonated isomers [cf. reaction (58)]... 

Chemical sensors based on amplifying fluorescent conjugated polymers functionalized, particularly, by crowns, thymine, or cyclophanes 07CRV1339. 

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