Silylation-mediated oxidation of dihydropyrimidine bases and nucleosides

✍ Scribed by James A. Kelley; Mohamed M. Abbasi; John A. Beisler

• Publisher: Elsevier Science
• Year: 1980
• Tongue: English
• Weight: 877 KB
• Volume: 103
• Category: Article
• ISSN: 0003-2697
• DOI: 10.1016/0003-2697(80)90257-2

✦ Synopsis

Vigorous trimethylsilylation

of dihydropyrimidine and dihydro-s-triazine bases and nucleosides results in their dehydrogenation to the analogous aromatic derivatives. This transformation, which cannot be effected by conventional dehydrogenating reagents, has been studied in detail using gas chromatographic and mass spectrometric methods. For 5,6-dihydro-5azacytidine

(ta) the oxidation is quantitative, requires molecular oxygen as well as reagents capable of both N-and O-silylation, is accelerated by heat and selected free radical initiators, and is inhibited by diethyldithiocarbamate and galvinoxyl free radical. This anomalous silylation reaction occurs on both an analytical and preparative scale. Silylation-mediated oxidation also exhibits a substantial deuterium isotope effect with preferential retention of deuterium at the new site of unsaturation. The potential of this new reaction for the synthesis of aromatic systems and for the insertion of nonexchangeable isotopic labels in suitable reduced precursors is illustrated.