The photodimer of thymine: an NMR study

Anet, Ragini

doi:10.1016/s0040-4039(01)99551-6

Cited by 32 publications

(11 citation statements)

References 15 publications

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“…This strong shielding effect by the analysis of their 13 C{H satellite proton on H 8 is caused by diamagnetic anisotropy of a spectra. 17,18 However, due to lack of these data, phenyl nucleus situated in front of the proton in anti configurations of 5 and 6 are characterized the syn head-to-tail configuration.…”

Section: Synthesis Of Dicoumarins (3 4) (Scheme 1)mentioning

confidence: 99%

Polyethers containing coumarin dimer components in the main chain. I. Synthesis by photopolymerization of 7,7?-(polymethylenedioxy) dicoumarins

Chen

Jean

1997

J. Appl. Polym. Sci.

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Eight 7,7-(polymethylenedioxy)dicoumarins were successfully synthesized by solution condensation of 7-hydroxycoumarin (umbelliferone) or 7-hydroxy-4-methylcoumarin (4-methylumbelliferone) with various dibromoalkanes. Upon benzophenone-sensitized irradiation with 350 nm light in dichloromethane, the terminal coumarin chromophores dimerize to form polyethers containing coumarin dimer components in the main chain. The configurations of the coumarin dimer linkages were characterized by 1 H-NMR spectra. For unsubstituted dicoumarins, the resulting polyethers consist mainly of syn and anti head-to-head coumarin dimer linkages. However, the configurations are syn and anti head-to-tail for those from 4-methyl-substituted dicoumarins. The highest reduced viscosity is 0.23 dL/g obtained with polyether from 7,7-(decamethylenedioxy)dicoumarin. The photopolymerization in dichloromethane obeys zero order and first order with respect to coumarin chromophore and benzophenone, respectively.

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Section: Synthesis Of Dicoumarins (3 4) (Scheme 1)mentioning

confidence: 99%

Polyethers containing coumarin dimer components in the main chain. I. Synthesis by photopolymerization of 7,7?-(polymethylenedioxy) dicoumarins

Chen

Jean

1997

J. Appl. Polym. Sci.

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“…This expectation in turn is based solely on a considerable body of evidence that the ANTI conformation is favored over the SYN in pyrimidine nucleosides, with an even stronger bias for ANTI in pyrimidine-5'-nucleotides due to the repulsion of the Zketo oxygen and the negatively charged phosphate in the SYN conformation. Interestingly, Weinblum and Johns (6) With few exceptions crystalline cyclobutane derivatives assume a puckered conformation which confers on the ring substituents quasi-axial (a) and quasi-equatorial (e) orientations ( Several groups (9,10,39), in their studies of photodimerized pyrimidine bases, have concluded that 5-6 Hz values for J,, are consistent only with a vicinal relationship for the two 6-hydrogens. However, four bond coupling constants of this magnitude have been observed for hydrogens which constitute an e,e pair in other cyclobutane ring systems (35,36).…”

Section: Spectral Assignmentmentioning

confidence: 99%

“…irradiation of thymine (2-4): In U.V. irradiated DNA the ' predominant photoproduct is formed from thymines adjacent on a polynucleotide strand and has been shown to possess the cis-syn geometry (6)(7)(8)(9)(10)(11)(12) with the trans-syn form as a minor product (13). Several groups have examined photodimer production in model compounds, particularly the dinucleoside mono- (Fig.…”

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confidence: 99%

A Proton Magnetic Resonance Study of the Ultraviolet Photoproduct of d(TpT) in Aqueous Solution

Hruska¹,

Wood²,

Ogilvie³

et al. 1975

Can. J. Chem.

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. Can. J. Chem. 53, 1193Chem. 53, (1975.The p.m.r. data of d(TpT) and its predominant U.V. photoproduct d(T[p]T) in aqueous solution are compared. The data are consistent with the presence of a cis-syn cyclobutane ring in d(T[p]T). Consideration of the H I z chemical shifts leads to the conclusion that changes in the sugar-base torsion angle of both nucleotide fragments of the parent molecule are required to bring the thymine bases into alignment for photodimerization. The coupling constants indicate that the conformation of the 5'-terminal fragment is only slightly affected by the cyclobutane ring formation. Photodimerization brings about a distortion of the sugar pucker in the 3'-terminal fragment. In this fragment both the gauche-gauche and gauche-trans con-I formers are significantly populated whereas the trans-gauche form is excluded. d(T[p]T) predominant. Les donnees sont en accord avec la presence d'un cyclobutane-cis-syn dans le d(T[p]T). L'examen des dkplacements chimiquesdu HI, conduit B la conclusion que des changements dans I'angle de torsion sucre-base des deux fragments du nucleotide de la mol6cule parente sont requis pour amener les bases thymines dans une orientation approprik pour-la photodimkrisation. Les constantes de couplage indiquent que la conformation du fragment 5' terminal n'est que tres peu affectee par la formation du noyau cyclobutanique. La photodimerisation amene une distorsion de la molkule de sucre plissk dans le fragment 3' terminal. Dans ce fragment, les deux conformeres gauchegauche et gauche-trans existent d'une f a~o n importante alors que la forme trans-gauche n'existe pas.[Traduit par le journal]

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“…Such a strong selective shift does not exist for the Hs absorption in syn head-tohead configuration. The anti head-to-head and headto-tail structures of several cyclobutanes have been characterized by the analysis of their ~3C-H satellite proton spectra [18,19]. However, due to the lack of data of our photo-cyclized products, anti configurations of 5_ and _6 are characterized by comparing with the results by Muthuralnu et al obtained in similar conditions [10].…”

Section: Structural Analysis Of Photo-cyclized Productsmentioning

confidence: 84%

Synthesis of polyesters containing coumarin dimer components by photopolymerization of 7,7?-coumarinyl polymethylene dicarboxylates

Chen

Hong

1994

J Polym Res

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Eight 7,7'-coumarinyl polymethylene dicarboxylates have been successfully synthesized by solution condensation of 7-hydroxycoumarin (umbelliferone) or 7-hydroxy-4-methylcoumarin (4-methylumbelliferone) with various polymethylene diacid chlorides. Upon benzophenone-sensitized irradiation with 350 nm light, the terminal coumarin chromophores dimerize to form intramolecular cycloadducts or intermolecular polyesters with three kinds of cyclobutanes (syn head-to-head, anti head-to-head, anti head-to-tail), depending on structure of the dicarboxylates and reaction conditions. The structures of the cycloadducts and polyesters have been characterized by ~H NMR spectra. When the methylene units exceed seven, intermolecular reaction becomes predominant and result in antirich configuration photo-cyclized products with higher viscosity. Lower polar solvents and 4-methyl substitution in coumarin chromophores also promote intermolecular reaction. The highest viscosity (rlrea = 0.42 dL/g) is obtained with polyester from 7,7'-(4-methyl coumarinyl) decamethylene decarboxylate. Irradiation of the polyesters with 254 nm light leads to symmetric cleavage of the cyclobutane linkage in the main chain.

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The photodimer of thymine: an NMR study

Cited by 32 publications

References 15 publications

Polyethers containing coumarin dimer components in the main chain. I. Synthesis by photopolymerization of 7,7?-(polymethylenedioxy) dicoumarins

Polyethers containing coumarin dimer components in the main chain. I. Synthesis by photopolymerization of 7,7?-(polymethylenedioxy) dicoumarins

A Proton Magnetic Resonance Study of the Ultraviolet Photoproduct of d(TpT) in Aqueous Solution

Synthesis of polyesters containing coumarin dimer components by photopolymerization of 7,7?-coumarinyl polymethylene dicarboxylates

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