A new method for the synthesis of nucleoside 2′,3′-O,O-cyclic phosphorodithioates via aryl cyclic phosphites as intermediates

The reaction of 5′-O-protected ribonucleosides with tri(4-nitrophenyl) phosphite in the presence of pyridine furnished rapid formation of the corresponding 4-nitrophenyl 2′,3′-O,O-cyclic phosphites which upon sulfhydrolysis, followed by sulfurization of the resultant cyclic H-phosphonothioate and removal of the 5′-O-protecting groups, afforded nucleoside 2′,3′-O,O-cyclic phosphorodithioates in high yields.