The Isomerization of Purine Nucleosides in a Dilute Alkaline Solution

摘要: A further study of the isomerization inosine (1a) in a dilute alkaline solution has revealed formation α-pyranbsyl isomer (4a) and its β-isomer (3a). Adenosine (1b) was isomerized at 130 °C for 12 hr pH 10, giving α-furanosyl (2b) (2% yield), β-pyranosyl (3b) (11%), α-pyranosyl (4b) (0.8%), respectively; 65% 1b also remained. 9-β-D-Ribopyranosyl-6-mercaptopurine (3c) prepared through this reaction from corresponding β-furanoside (1c). Arabinosyl or xylosyl purine nucleosides were isomerized, whereas neither 2′-deoxy nor 2′-substituted nucleoside showed any clear evidence isomerization. In conclusion, base 2′-hydroxyl anion are essential to nucleosides. By means NMR, both 4a 4b found have 1C conformation, while 3a 3b Cl conformation.