Functional monomers and polymers. CIV. Synthesis and properties of oligomer models of polyethyleneimine derivatives with spacer-separated nucleic acid bases

A series of polyethyleneimine derivatives and their oligomer models with pendant thymine or adenine bases separated by β-alanyl groups as spacers were prepared by an activated ester method. To elucidate the nature of intramolecular interaction of thymine and adenine bases ultraviolet (UV) spectrophotometric studies were undertaken for the series of compounds and the results were compared with those obtained for the corresponding oligomers without spacers. In the thymine derivatives, the nature of the intramolecular interaction resembled that of the corresponding compounds without β-alanyl units, although larger hypochromicities were found in the series with β-alanyl units. In the adenine derivatives, contrary to the corresponding thymine systems, UV hypochromicities of the compounds decreased by incorporation of the spacer group into side chains. It became evident that the intramolecular interaction of adenine bases was due to stacking neutral species, hydrogen bonding, and residual hypochromicity for the protonated species.     

Functional monomers and polymers. XCIII. Photochemical reactions on the acrylic and methacrylic copolymers containing thymine bases

Photodimerization of Polyacrylic and polymethacrylic derivatives with different pendant thymine unit content was studied in dimethylformamide solution. The quantum efficiency of thymine base for the photodimerization increased with increasing thymine content in the copolymers. The quenching study, which used isoprene as the quencher, revealed that the photodimerization resulted from excited singlet state increases with increasing thymine content. The photochemical results were discussed in terms of self-association of thymine bases in the polymer chain.     

Functional monomers and polymers. XCIV. Photochemical reactions on the synthetic polymers containing thymine bases in the presence of adenine derivatives

Photodimerization reactions of polyacrylate and polymethacrylate derivatives and the dimer model compound containing thymine bases were studied in the presence of adenine derivatives in dimethyl sulfoxide; N,N-dimethylformamide; and dimethyl sulfoxide–ethylene glycol solutions. The photodimerization of thymine bases both in the polymers and in the dimer model compound was found to be quenched by the addition of adenine derivatives. Base-base interaction in the ground state was also studied by ultraviolet (UV) spectroscopy in the three solvents. The quenching of the photodimerizationof thymine bases in the presence of adenine derivatives was discussed in terms of the specific interaction between adenine and thymine bases both in ground and excited states.     

Functional monomers and polymers. XXXXVI. A copolymerization study of methacryloyl-type monomers containing nucleic acid bases in chloroform solution

Behavior of the free radical copolymerization of N-β-methacryloyloxyethyl derivatives of adenine with that of thymine was studied in chloroform solution, taking account of the specific base-base interaction of these monomers. Hydrogen bonding interaction between such monomers was observed by NMR spectroscopy. The acceleration of copolymerization was found to be greater either at lower monomer concentration or at lower polymerization temperature. When N-β-methacryloyloxyethylcarbazole was used as a comonomer, the rate of copolymerization showed a similar trend as in the case of usual free radical copolymerizations. From r₁ and r₂ values obtained, the copolymerization was found to be alternating, particularly in the case of copolymerization between monomers having complementary nucleic acid bases. The results suggest that the hydrogen bonding interaction between adenine and thymine plays a role in the propagation step.     

Functional monomers and polymers. CLIV. Application of nucleic acid base containing polymers to high performance liquid chromatography

Poly-L -lysine (PLL) derivatives containing pendant nucleic acid base, such as thymine or adenine, were bonded successfully to 3-aminopropylsilanized silica (APS-silica) and silica gel. These resins were found to be useful as the column of high performance liquid chromatography (HPLC) for the selective separation of oligoethyleneimine derivatives having pendant thymine or adenine bases.     

Functional monomers and polymers. CVIII. Photodimerization of pendant thymine bases in thymine containing poly-lysine derivatives

The photodimerization reaction of pendant thymine bases in thymine-containing poly-lysine derivatives was studied over a wide range in aqueous solution. It was found that the quantum yield of the photodimerization of pendant thymine bases is affected mainly by the conformation of the polymers in solution. The differences in photoreaction behavior were discussed for poly-D -, poly-L -, and poly-DL -lysine derivatives.     

Functional monomers and polymers 159 synthesis and photochemical reactions of polymers containing thymine photodimer units in the main chain

Polyamides containing thymine photodimer units in the main chain were synthesized, and their photolysis by ultraviolet irradiation below 260 nm were studied in film state. Photodimers of thymine derivatives were obtained by photochemical reaction of the carboxylic acid derivatives of thymine in aqueous solution irradiated above 270 nm. An attempt was made to resolve the isomers of the photodimers, and the two kinds of cis isomers [cis–syn(head to head), and cis–anti(head to tail)] were isolated successfully. The polyamides were prepared by condensation of the photodimers with diamine using an activated ester method. The photodissociation of the thymine photodimer in the polymer main chain caused the breakage of the polymer chains, leading to the production of oligomers and dimer compounds containing thymine bases at the ends of the molecule. The dissociation rate of the polymer did not depend on the kind of the thymine photodimer which was in the main chain of the polymer.     

Functional monomers and polymers. XCVI. Photochemical reactions on oligo- and polyethyleneimines which contain pendant thymine bases

The photodimerization reaction of oligo- and polyethyleneimine derivatives which contain pendant thymine bases in various amounts was studied in aqueous solution in a wide pH range and in N, N-dimethylformamide solution. The photodimerization reaction of these derivatives in poly(methyl methacrylate) was also studied. It was found that its quantum efficiency tended to increase as thymine units were added to the oligomers and copolymers. This result is discussed in terms of the effect of the nearest neighboring thymine units and singlet energy migration, particularly in the polymers.     

N1-(2-furoylmethyl) and N1-(5-nitro-2- furoylmethyl) derivatives of uracil and its 5-substituted derivatives

The corresponding N₁-(2-furoylmethyl) and N₁-(5-nitro-2-furoylmethyl) derivatives of uracil and its 5-substituted derivatives were obtained by the reaction of 2-bromo- and 5-nitro-2-bromoacetylfurans with uracil, 5-fluorouracil, and thymine. The structures of these compounds as N₁-substituted uracils were proved by a study of the UV spectra at various pH values. The computational method of expanding the UV spectra into individual bands was used.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1268–1270, September, 1971.     

FORMATION OF CYCLOBUTANE THYMINE DIMERS PHOTOSENSITIZED BY PYRIDOPSORALENS: A TRIPLET-TRIPLET ENERGY TRANSFER MECHANISM

The 365 nm irradiation of thymine thin films in the presence of pyridopsoralens is shown to induce the formation of cyclobutane thymine dimers, in contrast to other compounds such as 8- and 5-methoxypsoralen. In order to elucidate the mechanism of such a photosensitized reaction, we have determined the energy of the lowest triplet state (T1) of these compounds, using phosphorescence spectroscopy and CNDO/S quantum chemistry calculations. The T1 energy values were found to be significantly higher for pyridopsoralens--up to 0.3 eV--than for 8- and 5-methoxypsoralen (approximately 2.8 eV), which are not able to photoinduce cyclobutane thymine dimers. The determination of the relative efficiency of cyclobutane thymine dimer formation was performed using chromatographic analysis. A good correlation was found between the energy of the T1 state of the psoralen derivatives and the related cyclobutane thymine dimer formation. Moreover, the photosensitized cyclobutane thymine dimer formation appeared to be temperature-dependent. Our results are consistent with a mechanism involving a triplet energy transfer from the pyridopsoralen to thymine.     

Reactive crystals. IV. Crystalline state photopolymerization of 5,5′-1,4-phenylene-bis(2-cyano-2,4-pentadienoic acid) derivatives

5,5′-1,4-Phenylene-bis(2-cyano-2,4-pentadienoic acid) derivatives were prepared. Many of this series of compounds were found to be polymerizable in the crystalline state by irradiation with light of wavelength λ > 340 nm. The polymers obtained contain a benzene and a cyclobutane ring in the main chain and have a cyanoacrylate as the side chain. They are crystalline and some of them are soluble in organic solvents. Photopolymerization was found to follow a stepwise mechanism. The polymerization process is separable into an oligomerization and a subsequent polymerization by controlling the wavelength of the irradiating light; an oligomer was obtained by an irradiating light; an oligomer was obtained by an irradiating light of wavelength λ > 430 nm.     

Characterization of a cross-linked DNA-Endonuclease VIII repair complex by electrospray ionization mass spectrometry

Electrospray mass spectrometry techniques were used to characterize components of the active site in Endonuclease VIII by identifying the amino acid sequence and the binding site for a tryptic peptide derived from Endo VIII in a cross-linked DNA-peptide complex. Endo VIII, a DNA repair enzyme with both glycosylase and lyase activities, was covalently bound to a thymidine glycol-containing oligodeoxynucleotide duplex by converting a transient Schiff base formed during the course of the glycosylase activity to a stable covalent bond by chemical reduction with sodium borohydride. After tryptic digestion of the initial product, the identification of the cross-linked peptide was deduced initially from the molecular mass of the tryptic product obtained by negative ion electrospray mass analysis. Nanospray tandem mass spectrometry (MS/MS) analysis of the tryptic product corroborated the molecular mass of the peptide fragment and verified the point of attachment to the oligomer, but failed to produce sufficient fragmentation to sequence the peptide completely. Direct evidence for the amino acid sequence of the peptide was obtained after enzymatic digestion of the DNA portion of the cross-linked DNA-peptide product and analysis by negative ion nanospray MS/MS. Examination of the ions from collision induced fragmentation disclosed that this substance was the N-terminal tryptic fragment of Endo VIII cross-linked to a portion of the oligomer, and that the N-terminal proline from Endo VIII was covalently bound to the residual deoxyribose moiety at the original location of the thymine glycol in the oligomer.     

Controllable synthesis of novel mono-and di-terpyridine derivatives

A series of novel mono-and di-terpyridine derivatives with purinyl and pyrimidyl group were obtained from the reaction of 4′-p- bromomethylpbenyl-2,2′:6,2″-terpyridine with 6-mercaptopurine,2,6-dimercaptopurine and thymine,respectively.The active hydrogens on these alkaloids could be abstracted stepwise using different bases,which made the addition controllable.     

Novel pyrimidine and pyrimido[1,2-a]pyrimidine derivatives. By-products of a guanidine based thymine synthesis

The isolation, structural elucidation, directed preparation and some derivatives of three previously unknown heterocycles is reported. Arising from a guanidine based thymine synthesis, these novel compounds exhibit substituted and fused pyrimidine structures repectively.     

Regioselective synthesis of 1-allyl- and 1-arylmethyl uracil and thymine derivatives

2,4-Bis(trimethylsiloxy) pyrimidines 1 with allyl halides and arylmethyl halides in 1,2-dichloroethane in the presence of I₂ regioselectively provide 1-allyl-/1-arylmethyl-uracil and thymine derivatives. The secondary aryl alkyl and diaryl methyl halides with 1 provide chiral 1-arylalkyl/1-(diarylmethyl) uracil/thymine derivatives. The procedure has been extended to the synthesis of fluorescent uracil/thymine derivatives.     

Polymerization of cyclic derivatives of uracil and thymine

Cyclic derivatives of uracil and thymine were synthesized from their corresponding 1-(2′-chloroethyl) derivatives by dehydrochlorination. These compounds were found to undergo a variety of reactions, giving many valuable derivatives of uracil and thymine. The cyclic derivatives, as monomers, were polymerized with a cationic initiator by a unique ring-opening process. The polymerization proceeded by ring opening with isomerization of the pyrimidine ring to give a polymer in which pyrimidine rings were connected with ethylene between N-1 and N-3 or O-4 in the pyrimidine ring. The structure of these polymers was determined by nuclear magnetic resonance (NMR), ultraviolet (UV), infrared (IR), and mass spectra. The structure was affected by polymerization temperature.     

A convenient, high-yield synthesis of 1-substituted uracil and thymine derivatives

Novel reagents for the synthesis of 1-substituted uracil and thymine derivatives have been developed. The aminolysis of 2- or 4-nitrophenyl 3-ethoxyacryloylcarbamate and 3-ethoxy-2-methylacryloylcarbamate with a variety of primary amino derivatives proceeded smoothly under very mild reaction conditions yielding almost quantitatively the 1,3-disubstituted urea derivatives. Their subsequent cyclization provided the 1-substituted uracil and thymine compounds, in almost quantitative yield.     

Intra- and intermolecular interactions in the series of acyclic and macrocyclic compounds containing nucleotide bases and their derivatives

Intra-and intermolecular interactions in acyclic compounds containing nucleotide base (uracil and thymine) derivatives and their macrocyclic analogs (pyrimidinophanes) were studied by IR, UV, luminescence, and NMR spectroscopy. Molecules of these compounds include one or two N³-methylsubstituted or N³-unsubstituted uracil fragment or two adenine fragments linked through a hexamethylene spacer to an uracil, 5,5′-methylenediuracil or diphenylmethane fragment. The examined compounds almost all are characterized by π-π interactions and intramolecular hydrogen bonding between the terminal uracil or adenine fragments. Intramolecular association constants were determined and factors affecting them were discussed. Complex formation of acyclic and macrocyclic ligands with adenine and thymine derivatives was studied. The low values of the association constants were interpreted in terms of a competition between intra-and intermolecular bonding and very labile ligand structure.     

Functional monomers and polymers. CII. Synthesis and properties of oligomer models of polyethyleneimine derivatives containing pendant adenine bases

A series of oligomer model compounds of polyethyleneimine derivatives with pendant adenine bases were prepared by the reaction of a carboxyethyl derivative of adenine with oligomeric amines, using an activated ester method. To evaluate the intramolecular interaction between pendant adenine bases in these compounds, ultraviolet spectra at various pH regions were measured. Ultraviolet hypochromicities and pK_a values depended linearly on the chain length of the oligomers. The results showed that the intramolecular interactions of adenine bases were realized less in their protonated than neutral forms.     

Convenient syntheses of 7-hydroxy-1-(hydroxymethyl)-3-(thymin-1-yl)-2,5-dioxabicyclo

Synthesis of the diastereoisomeric LNA (locked nucleic acid) nucleosides 1-(2-O,4-C-methylene-alpha-L-ribofuranosyl)thymine (6) and 1-(2-O,4-C-methylene-alpha-L-xylofuranosyl)thymine (13) are reported via convenient reaction cascades from di-O-p-toluenesulfonyl and tri-O-methanesulfonyl nucleoside derivatives 3, 7, and 10.