Nucleic acid related compounds. 81. Syntheses of 9-(3-deoxy-β-D-threo-pentofuranosyl)adenine, the core nucleoside of the extraordinarily selective antibiotic agrocin 84, and simplified structural component analogues†‡

Alternative syntheses of 9-(3-deoxy-β-D-threo-pentofuranosyl)adenine (4), the core nucleoside of agrocin 84 [and its 2′-deoxy threo isomer 5] were devised: (1) direct conversion of 9-(β-D-arabinofuranosyl)adenine into 9-(2,3-anhydro-β-D-lyxofuranosyl)adenine and regioselective opening of its oxirane ring with sodium borohy-dride to give 4 and 5(˜7.5:1); (2) treatment of adenosine with sodium hydride and 2,4,6-triisopropylbenzene-sulfonyl chloride, and subjection of the resulting 2′(3′)-sulfonates to the reductive [1,2]-hydride shift rearrangement with lithium triethylborohydride to give 4 and 5 (˜ 2:1); and (3) subjection of the phenoxythiocar-bonyl esters of 9-[2(3),5-bis-O-(tert-butyldimethylsilyl)-β-D-arabinofuranosyl]adenine to Barton deoxygenation, and deprotection to give 4 and 2′-deoxyadenosine (˜5:1). Methods (2) and (3) gave lower yields. Syntheses of simplified 6-N- and 5′-O-adenosine phosphoramidate model compounds were explored to examine potential access to such features in the structure proposed for agrocin 84.