Synthesis and physico-chemical properties of alternating copolymers of maleic anhydride with dihydropyrans containing 6-chloropurine, 6-mercaptopurine, and hypoxanthine .8.

The new monomers, 2-(6-chloro-, 6-hydroxy-, 6-mercapto-, and 6-aminopurin-9-ylmethyl)-3,4-dihydro-2H-pyran (3a, 3b, 3c, and 3d, respectively) and 2-(6-chloro and 6-hydroxypurin-7-ylmethyl)-3,4-dihydro-2H-pyran (4a and 4b, respectively) were synthesized. Copolymerization of these monomers with maleic anhydride resulted in the alternating copolymers 5 and 7, which were hydrolysed to give poly[(2-(6-Cl-, OH-, and SH-purin-9-ylmethyl)tetrahydropyran-5,6-diyl) (1,2-dicarboxyethylene)])(6a, 6b, and 6c, respectively) and poly[(2-(6-Cl- and OH-purin-7-ylmethyl) tetrahydropyran-5,6-diyl) (1,2-dicarboxyethylene)] (8a and 8b, respectively). The polymers 6 and 8 are polynucleotide analogues, which have 6-chloropurine, hypoxanthine or 6-mercaptopurine as nucleic acid bases. They showed physico-chemical properties quite similar to those of the natural polynucleotides, e.g. polymer 6b showed 23.7% of hypochromicity of the u.v. absorption at a wavelength of 250 nm, and 8b exhibited a broad excimer fluorescence around 422 nm and showed typical polyelectrolyte behaviour.