N -dA adduct

Benzo[a]pyrene diol epoxides react with adenine residues in DNA to give 105(-l-)- and 10R(-)-tra s-anti-benzo[a]pyrene-N -dA adducts (103), lOR(-) shown, which give rise to mutational hot spots. The solution structure of an 11-mer duplex in which there is a modified adenine has been studied, and it was... 

Also, in contrast to the trans-anti-B P-N -dA adducts, neither the IS (-)-trows nor the 1R (+)-trans-anti-B[c]Ph-N6-dA adducts destabilize double-stranded DNA since the ATm = 0°C [115]. The other fjord region adducts studied, trans-anti-B[g]C-.N6-dA and trons-anti-DB[a,f]P-.N6-dA, are also NER-resistant (Figure 12.8) [113]. Both... 

In summary, our hypothesis is that the increased polycyclic aromatic ring-base stacking interactions in the fjord region PAH diol epoxide-N -dA adducts stabilize the duplexes and inhibit the extent of strand opening in XPC/HR23B complexes that is critically important for successful NER [38], possibly by preventing the flipping out of nucleotides from the complementary strand. 

A few syntheses of alkenic nitrogen compounds based on the rDA reaction are known. For example, ynamine (19), via rDA decomposition under FVP conditions, gives l-N,N-diethylamino-3-buten-l-yl (20). 2-Vinylimidazoles had previously been obtained by lengthy reaction schemes with low yields however, a practical laboratory synthesis of 2-vinylimidazoles based on a DA-rDA scheme has been developed. The DA adduct of acrolein and cyclopentadiene was converted to 2-(5-norbomen-2-yl)imida-zole (21), which was readily transformed into 2-vinylimidazole (22) as depicted in equation (16). Glyoxal gave the best result, but other a-dicarbonyl compounds could be substituted to obtain various 2-vinylimidazoles. 

Cosman, M., Fiala, R., Hingerty, B.E., Laryea, A., Lee, H., Harvey, R.G., Amin, S., Geadntov, N.E., Broyde, S., and Patel, D. (1993) Solution conformation of the (+)-traus-anti-[BPli]dA adduct opposite dT in a DNA duplex intercalation of the covalently attached benzojcjphenanthrene to the 5 -side of the addud site without disruption of the modified base pair. Biochemistry, 32, 12488-12497. 

Transcription past (+)- or (-)-tmns-anti-N6-B[c]Y>hDE-dA adducts by T7 RNA polymerase and RNA Pol II has also been examined. T7 RNA polymerase is able to bypass each stereoisomer when either is located on the template strand, and a significant ladder of truncated transcripts is observed [59]. Furthermore, the -)-trans-anU-/ / -IS[ i P h DIi-dA poses a stronger block to the phage polymerase when compared to the (+)-trans-anti-N6-B[c]PhDE-cLA In addition, the terminal base incorporated at the 3 -end opposite the adduct is more often a guanine than the expected uracil. In contrast, transcription past the two N6-li c]PhDE-dA stereoisomers by RNA Pol II resulted in a small percentage of read-through, with less than 20% bypass [90]. While no data are available for the base incorporated at the 3 -end of the truncated N<5-B[c]PhDE-dA transcripts, all truncated RNA molecules appear to be the same length. 

We observed in Chapter 4 that unlike furan and thiophene derivatives, N-alkylpyrroles fail to form a DA adduct. Thus, from iV-methylpyrrole, an alkylation product 105 is isolated.Thus electrophilic substitution is the primary course of the reaction. (Also see Chapter 4.)... 

Even HALS compounds which absorb weakly at 337 nm can be analysed directly without matrix assistance, with the exception of the high-MW Hostavin N 30 (ca. 1500 Da), which fragments by direct laser desorption ionisation of intact molecules occurs only in the presence of a (dithranol) matrix. Direct laser desorption leads only to noncharacteristic, low-MW fragments. Hostavin N 20 leads to [M + H]+, [M + Na]+, [M + K]+ and some fragmentation peaks. MALDI-ToFMS of Tinuvin 765, which consists of a mono- and bifunctional sterically hindered amine, only shows the adduct peaks of the bifunctional amine apparently, the monofunctional amine is not ionisable. 

Marchesan S, Da Ros T, Prato M (2005) Isolation and characterization of nine tris-adducts of N-methylfulleropyrrolidine derivatives. J. Org. Chem. 70 4706 1713. 

Coulembier O, Lohmeijer BGG, Dove AP, Pratt RC, Mespouille L, Culkin DA, Benight SJ, Dubois P, Waymouth RM, Hedrick J (2006) Alcohol adducts of N-heterocyclic carbenes latent catalysts for the thermally -controlled living polymerization of cyclic esters. Macromolecules 2006 5617-5628... 

The optical properties of the 8-o-PhOH-purine adducts have provided insight into their ground-state structures at the nucleoside level. These adducts have the ability to phototautomerize, through an excited-state intramolecular proton transfer (ESIPT) process, to generate the keto form. This tautomerization depends on the presence of a intramolecular hydrogen (H)-bond between the phenolic OH and the imine nitrogen (N-7). Figure 14 shows normalized absorption and emission spectra for 8-o-PhOH-dG and 8-o-PhOH-dA in aqueous buffered water and hexane. In water, 8-o-PhOH-dG shows only enol emission at 395 nm, while 8-o-PhOH-dA shows enol emission at 374 nm and phenolate emission at 447 nm. In hexane, both adducts show keto emission at 475 nm 8-o-PhOH-dA also shows a small amount of enol emission and no phenolate emission. These results show that in water, the intramolecular H-bond... 

Diepoxybutane also reacts with nucleosides, nucleotides and DNA. Adducts at N of adenine were identified in incubations (pH 7) containing deoxyadenosine, deoxyadenosine monophosphate or poly(dA-dT)(dA-dT), as determined by mass spectrometry, or calf tliymus DNA as determined by a high-performance liquid chromatography/ 32P-postlabelling method (Leuratti et al., 1994). By the latter method, the authors demonstrated adduct formation to N of adenine in DNA from Chinese hamster ovary cells incubated with diepoxybutane at 37°C. 

In the case of amines, protonation that withdraws electron density from the center of reaction lowers the rate of reaction by a factor of 30 (Das and von Sonntag 1986). Besides H-abstraction from carbon [reactions (18) and (21)], the formation of N-centered radical cations is observed [reactions (19)/(22) and (20) for amino acids see, e.g Bonifacic et al. 1998 Hobel and von Sonntag 1998]. Reaction (20) is also an H-abstraction reaction. The ET reaction (19)/(22) may proceed via a (bona-fide, very short-lived) adduct (Chap. 7). 

Many rDA reactions are carried out at temperatures of 150 C or more in solution phase and often at temperatures of 400-600 C using the flash vapor pyrolysis (FVP) method individual conditions are referenced throughout the text. However, an accelerating effect by anionic, cationic and radical substimtion on either the dienophile or at the termini of the diene fragments has been predicted by Carpenter.Experimentally, this prediction has been substantiated only for anionic substitution. In 1967, Hart reported what is likely the first example of an oxyanion-accelerated rDA reaction. Both oxyanionic " and car-banionic substituents accelerate the cycloreversion reaction such that they proceed rapidly at room temperature (for example, equation 3). In addition, acid-catalyzed rDA reactions have been reported in which protonation effectively makes the dienophile fragment of the adduct more electron deficient. Grieco has utilized a room temperature retro aza DA reactitm useful for the N-methylation of dipeptides and amino acid derivatives (equatitm 4). ... 

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