Covalent analogues of DNA base-pairs and triplets. Part 3: Synthesis of 1,4- and 1,3-bis(purin-6-yl)benzenes and 1-(1,3-dimethyluracil-5-yl)-3 or 4-(purin-9-yl)benzenes

The Stille cross-coupling reactions of 1,4- and 1,3-bis(trialkylstannyl)benzenes or with 9-benzyl-6-chloropurine () led either to mono-coupled 4- or 3-[(tributylstannyl)phenyl]benzenes and or to bis(9-benzylpurin-6-yl)benzenes ( or ) depending on the ratio of the starting compounds, nature of the stannane and conditions. Analogous reaction of with benzene-1,4-diboronic acid gave selectively in good yield. The reaction of stannanes with 1,3-dimethyl-5-iodouracil gave 1-(9-benzylpurin-6-yl)-4- or -3-(1,3-dimethyluracil-5-yl)benzenes ( and ) in low yields. Compounds and are novel types of covalently linked analogues of nucleobase-pairs.