9-(β-D-Arabinofuranosyl) adenine 5'-phosphate was obtained from adenosine 5'-phosphate via the novel intermediate 8, 2'-O-cycloadenosine 5'-phosphate. In contrast to the synthesis of 9-(β-D-arabinofuranosyl) adenine, it was difficult to cleave this compound by hydrogen sulfide directly to 8, 2'-O-cycloadenosine 5'-phosphate because of a considerable degree of dephosphorylation. However N-acylated 8, 2'-O-cycloadenosine 5'-phosphate was readily cleaved at the cyclo-bond by hydrogen sulfide. Desulfurization of 8-mercapto-9-(β-D-arabinofuranosyl) adenine 5'-phosphate gave the desired pure crystalline product.'
