Synthesis of 2′-Deoxyisoinosine and Related 2′-Deoxyribonucleosides

Various 2-substituted purine and pyrrolo2,3-d]pyrimidine 2′-deoxyribonucleosides with methylthio ( 13a ), chloro ( 13b ), methoxy ( 9b ), and oxo ( 2, 3 ) substituents at C(2) are prepared. They are obtained either via stereoselective nucleobase-anion glycosylation or by base transformation. A three-step synthesis of the unknown 2′-deoxyisoinosine ( 2 ) from 2′-deoxyguanosine ( 15 ) is described. Compound 2 as well as its 7-deazapurine derivative 3 exhibit strong fluorescence.