2′‐Deoxyisoguanosine and Base‐Modified Analogues: Chemical and Photochemical Synthesis

Abstract

Abstract The synthesis of 2′‐deoxyisoguanosine ( 2 ), and the pyrrolo[2,3‐ d ]pyrimidine and pyrazolo[3,4‐ d ]pyrimidine 2′‐deoxyribonucleosides 3 and 4 is described. Condensation of the imidazole precursor 5 with benzoyl isocyanate followed by reaction with ammonia gave 2 . Its N(7) regioisomer was obtained from 6 . Compound 2 was also prepared by the photochemically induced conversion of 2‐Chloro‐ and 2‐bromopurine 2′‐deoxyribofuranosides 9a and 10 , respectively, in aqueous solution, The photo reaction was further used for the synthesis of the compounds 3 and 4 starting with the amino‐chloro‐2′‐deoxynucleosides 9b and 9c , respectively.