Synthesis of 6-(2-thienyl)purine nucleoside derivatives that form unnatural base pairs with pyridin-2-one nucleosides

Unnatural bases. 2-amino-6-(2-thienyl)purine and 2-amino-6-(2-furanyl)purin e, were newly designed to replace the previously developed purine analogue, 2-amino-6-(N,N-dimethylamino)purine. which specifically pairs with pyridin -2-one. These nucleoside derivatives were synthesized via the 6-substitutio n of 6-iodopurine nucleosides with tributylstannylthiophene or tributylstan nylfuran. As compared with 2-amino-6-(N,:V-dimethylamino)purine, 2-amino-6- (2-thienyl)purine reduced the interference in the stacking interactions wit h the neighboring bases in a DNA duplex and improved the efficiency of the enzymatic incorporation of the nucleoside triphosphate of pyridin-2-one opp osite the unnatural base. (C) 2001 Elsevier Science Ltd. All rights reserve d.