Thymidine with carbonyl

The formation of the activated intermediate for the AE with R -NH-R is accelerated by the addition of a proton or Lewis acid to the 2-carbonyl group in 151. This is necessary for aminations of uridine (150) or thymidine (162) with weakly basic amines such as aniline, e.g., to 161e (Section III, A). Silylated hydroxy-N-heterocycles lacking such an activating conjugated carbonyl group, however, usually react only with amines when a Lewis acid is present (Section III,A). 

The high reactivity of [A5b] is found back in the 5 -deoxy-5 -(1 thyminyl)thymidine which with equal ease as [45b] on irradiation results in a cls-syn dimer with the carbonyl groups cis to the furane oxygen (115). 

Photocycloadditions also proceed to give predominantly endo products. For example, the light-induced dimerization of thymidine occurs with endo selectivity. The carbonyl group of one ring positions itself over the other ring, and the more sterically crowded stereoisomer is obtained. 

Figure 6 An illustration of the proposal made by Schulze et al/ to explain the different loop conformations of [d(G4T4G4)in the Na form versus the similar NH4 and forms. (A) Na ions are coordinated in the plane of the outer G-quartets of [d(G4T4G4)]2, where additional coordination is possible with 02 carbonyls of thymidine loop residues. (B) The larger NH4 (right) is coordinated between G-quartets, where interaction with loop resides is not possible. This difference in cation coordination apparently contributes to the loops of the Na form being less mobile than in the Kf form. Additionally, the base of loop residue T8 in the NH4 and forms, in the absence of steric clash with T7, stacks directly on the base of residue G9...

CDAA (N-N-diallyl-2-chloroacetamide) was reported to reduce mitosis in barley (Hordeum vulgare L.) roots nearly 90% after 96 h at 57 yM (38). Propachlor (2-chloro-N-isopropylacetanilide) totally inhibited mitosis in onion (Allium cepa L.) root tips after an 18 h treatment with 75 yM (3 ). At 20 yM cell division was reduced approximately 50% and cell enlargement was reduced 40% in oat coleoptiles (39). After 24 h, 100 yM ioxynil (4-hydroxy-3,5-diiodobenzonitrile) reduced the mitotic index in broad bean (Vicia faba L. ) and pea root tips ( ). Few herbicides that inhibit cell division have been studied in adequate detail to locate the site of the block. A notable exception is the herbicide chlorsulfuron (DPX 4189, 2-chloro-N- [(4-methoxy-6-methyl-l,3,5-triazin-2-yl)amino]carbonyl -benzenesulfonamide) ( ). Ray reported a 50% reduction in corn growth 3 h after treatment with 28 yM chlorsulfuron. Mitosis in broad bean root tips was significantly reduced by 2.8 yM, whereas in three different tests, cell enlargement was not influenced with concentrations of 28 yM. Thymidine incorporation into DNA was inhibited in corn root tips after a 1 h treatment with... 

As for Ino which lacks one carbonyl group at the C(2) position of dT, the affinity with 10 is smaller (log K = 5.7) than that predicted from the amide value of 8.75, as found with 8. This fact again supports the notion that direct and/or indirect hydrogen bonding by the two exocyclic carbonyl groups of the thymidine derivatives serves to supplement the thermodynamic stability of the ternary complexes in aqueous solution. 

The value of — 22.6 0.6 kj mor obtained is similar to that of other hemi-acetal phosphoric esters. Treatment of 4-( -acetyl-2,3-< -carbonyl-a-L-rhamno-pyranosyl bromide with dibenzyl phosphate-triethylamine, followed by deprotection, yielded j3-L-rhamnopyranosyl phosphate. The same paper contains a synthesis of thymidine 5 H/ L fhamnopyranosyl)pyrophosphatc. Long-chain (C10-C16) alkyl 0-D-glucopyranosyl phosphates have been prepared via the orthoester method and described as novel anionic detergents. The MacDonald procedure (anhydrous phosphoric acid in vacuo at 56-60 for 2 h) has been used to convert di- and tri-saccharides into their a-glycosyl phosphates. The syntheses and n.m.r. of 2-acetamido-2-deoxy-D-glucose 1-, 3-, 4-, and 6-phosphates have been published. The chemical shifts were studied with respect to the position of the phosphate group D-Ribofuranosyl ribitol... 

The other two pyrimidine nucleobases, i.e., the uracil and thymine residues (Figure 1), bind strongly to metal ions only after deprotonation of their (N3)H site [87]. This means that carbonyl groups interact significantly with metal ions only if a suitable primary binding site is available (Section 3.3). To establish a sound basis for comparisons equilibria (7a) and (8a) were studied for several metal ion complexes of (N3)H-deprotonated uridine-type ligands (U), i.e., 5-fluorouridine, 5-chloro-2 -deoxyuridine, uridine, and thymidine (= 2 -deoxy-5-methyluridine). Plots of log K. 

Substitution of various nucleotides by 4 -thio-ribonucleotides into an siRNA sequence led to increased thermal and nuclease resistance, resulting in a longer term RNAi effect. A series of thymidine derivatives has been reported bearing C4 -carbo3q l-, metho q carbonyl-, carbamoyl-and methylcarbamoyl-substituents and evaluated for hybridisation properties with complementary DNA and RNA. Of note was a C4 -carbo)q -derivative that adopted an S-conformation resulting in an increase in thermal stability with RNA. ° 4 -C-Aminomethyl-2 -0-methylthymidine triphosphate has been shown to be incorporated into DNA using the thermophilic DNA polymerases Pfu and Therminator III. The incorporation of the C4 -modification resulted in an increased resistance towards exonuclease activity compared with the known 2 -0-methyl modification. ... 

---