Synthesis of a hydrogen-bond-degenerate tricyclic pyrrolopyrimidine nucleoside and of its 5′-triphosphate

Abstract

The syntheses of a number of 7-(2-deoxyribofuranosyl)pyrrolo[2,3-d]pyrimidine derivatives are described. Of these the 2-methylsulfanyl-4-hydroxy-5-acetoxyethyl derivative 7 was conveniently formed by condensation of 2-methylsulfanyl-4-hydroxy-6-aminopyrimidine with 2-chloro-4-acetoxybutanal 6; it was then converted to the 4-chloro derivative 12 with phosphoryl trichloride and coupled to 3,5-di-p-toluoyl-2-deoxy-α-ribosyl chloride. Transformation to the 5-aminooxyethyl derivative and ring closure of the latter gave the tricyclic 2-(2-deoxyribosyl)-4-methylsulfonyl-7-oxa-2,3,5,6-tetraazabenz[cd]azulene. Hydrazinolysis of the methylsulfonyl residue, then mercury(II) oxide oxidation, led to the target nucleoside 4. For its study as a polymerase substrate for incorporation into DNA the 5′-triphosphate was synthesised.