Seven-membered cyclic phosphate: synthesis and properties of S-cycloadenosine 2',5'-cyclic phosphate and cordycepin 2',5'-cyclic phosphate. Studies of nucleosides and nucleotides. LXIV. 1). Purine cyclonucleosides 25.

8,3'-Anhydro-8-mercapto-9-beta-D-xylofuranosyladenine (8,3'-s-cycloadenosine) was phosphorylated with cyanoethyl phosphate and DCC to 5'-phosphate. After 6-amino group was benzoylated, the monophosphate was treated with DCC to give a cyclic phosphate (II). The structure of compound II was elucidated as 8,3'-s-cycloadenosine 2',5'-cyclic phosphate by UV, NMR and CD spectra, as well as enzymatic hydrolyses. When compound II was desulfurized with Raney nickel, cordycepin 2',5'-cyclic phosphate (III) was obtained. Although compound III could be obtained from cordycepin 5'-phosphate with DCC, the yield was extremely low.