Synthesis of sugar-modified 2,6-diaminopurine and guanine nucleosides from guanosine via transformations of 2-aminoadenosine and enzymatic deamination with adenosine deaminase

Abstract

Treatment of 2,6-diaminopurine riboside (2-aminoadenosine) with α-acetoxyisobutyryl bromide in acetonitrile gave mixtures of the trans 2′,3′-bromohydrin acetates 2. Treatment of 2 with zinc–copper couple effected reductive elimination, and deprotection gave 2,6-diamino-9-(2,3-dideoxy-β-D-erythro-pent-2-enofuranosyl)purine (3a). Treatment of 2 with Dowex 1 × 2 (OH−) resin in methanol gave the 2′,3′-anhydro derivative 4. Stannyl radical-mediated hydrogenolysis of 2 and deprotection gave the 2′-deoxy 6a and 3′-deoxy 7a nucleosides. Treatment of the 3′,5′-O-(tetraisopropyldisiloxanyl) derivative (5a) with trifluoromethanesulfonyl chloride – 4-(dimethylamino)pyridine gave 2′-triflate 5c. Displacement with lithium azide–dimethylformamide and deprotection gave the arabino 2′-azido derivative 8a, which was reduced to give 2,6-diamino-9-(2-amino-2-deoxy-β-D-arabinofuranosyl)purine (8b). Sugar-modified 2,6-diaminopurine nucleosides were treated with adenosine deaminase to give the corresponding guanine analogues. Keywords: adenosine deaminase, 2,6-diaminopurine nucleosides, deoxygenation, guanine nucleosides, nucleosides.