Cyclic phosphates of formycin

The syntheses of N1- and N2-isopropylformycin (10, 11), formycin 3',5'-cyclic and 2',3'-cyclic phosphate (3,7) and their N-methyl and N-isopropyl derivatives (13, 15, 19, 23) are described. It was observed that substitution at N1 or N2 with a bulky alkyl group or cyclic phosphorylation of the ribose moiety made formycin resistant to adenosine deaminase.