Preparation of 8,5'-O-cycloadenosine derivatives by reaction of 2',3'-O-isopropylideneadenosine with phenyl chloroformate or p-toluyl chloride.

Reaction of 2',3'-O-isopropylideneadenosine with p-toluyl chloride in a mixture of methylene chloride and triethylamine afforded 2',3'-O-isopropylidene-N,N,5'-O-tri-p-toluyladenosine (8)(30%), 8,5'-O-cycloadenosine derivatives 9 (34%) and 10 (11%), and a cyanoimidazole nucleoside 11 (12%).