Experimental methods have been devised for the permethylation of both adenosine (la® lb) and guanosine (2a®1- 2b + 3a) employing trimethylanilinium methoxide (TMAM). Reaction of the TMAM reagent with inosine (5a) and xanthosine (11) was found to promote imidazole ring and/or riboside cleavage (e.g., 5a®7a and 10). While methylation of inosine resulted in a variety of such reaction pathways, xanthosine followed essentially a single direction, leading to caffeine (12) as the major product. Reaction conditions developed for permethylation of these purine nucleosides with the TMAM reagent should prove useful with other such heterocyclic glycoside systems.
ASJC Scopus subject areas
- Organic Chemistry