Some C-ribo-nucleosides having typical aromatic heterocycles as base moiety were synthesized from the stereoselective addition of lithium salt of aromatic heterocycles to the protected d-ribose followed by the stereospecific cyclization under Mitsunobu conditions.
Abstract Cycloaddition of 2-(β- d -ribofuranosyl)furan ( 1 ) with maleimide followed by treatment with acetone-TsOH gave a mixture of four diastereomers 3a–d , which were separated by preparative t.l.c. The absolute stereochemistry of each was determined. The endo ( 3a and 3b )/exo ( 3c and 3d ) ratio of cycloadducts was ∼11:1 and the ratio of 3a (1 R ,4 S ) and 3b (1 S ,4 R ) was ∼3:1. The Diels-Alder