Nucleic Acid Related Compounds. 5. The Transformation of Formycin and Tubercidin into 2′- and 3′-Deoxynucleosides

Reaction of tubercidin (4-amino-7-β-D-ribofuranosylpyrrolo[2,3-d]pyrimidine) (1) with α-acetoxyisobutyryl chloride in the presence of excess sodium iodide in acetonitrile gave an acylated iodo intermediate (2) which was converted into 3′-deoxytubercidin (4) by hydrogenolysis and subsequent saponification.Analogous treatment of formycin (7-amino-3-β-D-ribofuranosylpyrazolo[4,3-d]pyrimidine) (5) gave 3′-deoxyformycin (6) and 2′-deoxyformycin (7) in an approximate ratio of 3:2. These purified nucleosides, 6 and 7 were individually deaminated enzymatically to give 3′-deoxyformycin B (8) and 2′-deoxyformycin B(9).Biological rationale, n.m.r., and mass spectra of these antibiotic-derived deoxynucleosides are discussed.