Abstract
IRRADIATION of a frozen aqueous solution of thymine with 254 nm light resulted in the formation of a cyclobutyl dimer of thymine (T=T)1–3. An analogous uracil dimer (U=U) is formed when uracil is irradiated under similar conditions1,4. These results are of great importance in understanding the photochemistry and photobiology of nucleic acids (reviews, refs. 2,5,6). Thus much work has been carried out on the mechanistic study of the photodimerization of pyrimidines7. The photodimerization of α,β-unsaturated ketones may be examined similarly. As part of these studies the four dimers of 6-methyl-uracil (6 MU), for example, cis-syn, cis-anti, trans-syn and trans-anti, have been isolated in a pure state from 6 MU under a variety of conditions. The stereoconfigurations of these dimers of 6 MU=6 MU have been assigned (unpublished work) using techniques such as NMR, IR and chemical reactivities; however, the complete three-dimensional structure can only be determined by X-ray diffraction analysis. The crystal and molecular structure of a cis-syn type of 6 MU=6 MU has recently been reported8. In this communication we report the X-ray diffraction study of the cis-anti isomer.
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AMZEL, L., AVEY, H., BECKA, L. et al. Crystal and Molecular Structure of a 6-Methyluracil Photodimer. Nature New Biology 238, 204 (1972). https://doi.org/10.1038/newbio238204a0
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DOI: https://doi.org/10.1038/newbio238204a0