Nucleic acid related compounds. 25. Syntheses of arabino, xylo, and lyxo-anhydro sugar nucleosides from tubercidin ribo-epoxide

Treatment of the trans iodohydrin acetate, 4-amino-7-(3-iodo-3-deoxy-2-O-acetyl-5-O-[2,5,5-trimethyl-1,3-dioxolan-4-on-2-yl]-β- D -xylofuranosyl)pyrrolo[2,3-d]pyrimidine ( 2 ) with metha-nolic ammonia gave 2′,3′-anhydrotubercidin ( 3 ) in 96% yield. N 4 ,N 4 ,O 5 ′-Tribenzoylation of 3 gave 4 , which is stabilized against intramolecular cyclization. Treatment of 4 with boron tri-fluoride etherate (3′,5′-benzoxonium ion formation) followed by deblocking gave 4-amino-7-β- D -xylofuranosylpyrrolo[2,3-d]pyrimidine ( 5 ) in 91% overall yield from tubercidin ( 1 ). The 3′,5′-O-isopropylidene derivative ( 6 a) of 5 was mesylated to give 6 b which was deprotected in acid and the resulting trans hydroxy mesylate was treated with base to give 4-amino-7-(2,3-anhydro-β- D -lyxofuranosyl)pyrrolo[2,3-d]pyrimidine ( 7 ). This lyxo epoxide was treated with sodium benzoate in DMF to give 4-amino-7-β- D -arabinofuranosylpyrrolo[2,3-d]pyrimidine ( 8 ). Biochemical, spectroscopic, and chemical properties of these semisynthetic antibiotic analogues of biologically active adenine nucleosides are discussed.