SYNTHESIS OF IMIDAZO[1,2-A]PYRIDINE C-NUCLEOSIDES WITH AN UNEXPECTED SITE OF RIBOSYLATION

Several new polychlorinated imidazo[1,2-alpha]pyridine C-nucleosides h ave been prepared. Lithiated imidazo[1,2-alpha]pyridines were condense d with protected ribonolactones, trapped as 1'-acetoxy derivatives, an d these 1'-acetoxy derivatives were reductively deacetoxylated and dep rotected to give C-nucleosides. Long-range proton-carbon decoupling ex periments were used to determine the actual site of ribosylation and e stablished that the ribose moiety was unexpectedly attached to the C5 position of the imidazo[1,2-alpha]pyridines. This method has provided C-nucleosides, such as 5-(beta-D-ribofuranosyl)imidazo[1,2-alpha]pyrid ine and 5-(beta-D-ribofuranosyl)imidazo[1,2-alpha]pyridine and the cor responding alpha-products.