Cyclization by free radical addition of stannyl or thiyl radical to 3′-β-ethynyl uridine. Is the 3′-β-ethynyl group a spin trap in ribonucleotide reductase?

Abstract

Reaction of a stannyl or a thiyl radical, generated in situ with AIBN, on (2′-5′-di-O-tert-butyldimethylsilyl-3′-C-ethynyl-β-D-ribofuranosyl)uracil ( 2) gave in 60% and 17% yield respectively cyclized adducts 3 and 4 where the vinylic radical, formed by addition of stannyl or thiyl radical to the triple bond, reacted with the base. The 3′-β-ethynyl uridine di- and triphosphates could be a spin trap of the transient thiyl radical of ribonucleotide reductases.