Conformational Analysis of Some Radiation-Induced Decomposition Products of Thymidine Using 13C NMR Analysis

✍ Scribed by M. Bardet; J. Cadet; J. R. Wagner

• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: English
• Weight: 501 KB
• Volume: 34
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/(sici)1097-458x(199608)34:8<577::aid-omr940>3.0.co;2-n

✦ Synopsis

The "C NMR spectra of several diastereomers of radiation-induced decomposition products of thymidine and thymine (its homologue without a sugar moiety at N-1) were interpreted in terms of the conformational features of the pyrimidine ring. The study was based on the analysis of the changes in "C chemical shifts of the pyrimidine ring due to through-space interactions between the different substituents. First, y effects between the substituents at C-6 (hydroxyl, hydroperoxyl or 2,2,4,4-tetramethylpiperidone-N-oxyl) and the methyl group at C-5 were considered. Then these steric effects were combined with hydrogen bonding interactions between the hydroxyl group at C-5 and the carbonyl at C-4. This made it possible to account for the observed changes in the 13C chemical shifts of the pyrimidine ring. The 5,6-saturated pyrimidine moiety is proposed to adopt a half-chair conformation with the substituent at carbon C-6 in a pseudo-axial position.