Facile Synthesis of 2′‐Deoxyisoguanosine and Related 2′,3′‐Dideoxyribonucleosides

The 2′‐deoxyisoguanosine ( 1 ) was synthesized by a two‐step procedure from 2′‐deoxyguanosine ( 5 ). Amination of silylated 2′‐deoxyguanosine yielded 2‐amino‐2′‐deoxyadenosine ( 6 ) which was subjected to selective deamination of the 2‐NH 2 group resulting in compound 1 . Also 2′,3′‐dideoxyisoguanosine ( 2 ) was prepared employing the photo‐substitution of the 2‐substituent of 2‐chloro‐2′,3′‐dideoxyadenosine ( 4 ). The latter was synthesized by Barton deoxygenation from 2‐chloro‐2′‐deoxyadenosine ( 3 ) or via glycosylation of 2,6‐dichloropurine ( 12 ) with the lactol 13 . Compound 1 was less stable at the N‐glycosylic bond than 2′‐deoxyguanosine ( 5 ). The dideoxynucleoside 2 was deaminated by adenosine deaminase affording 2′,3′‐dideoxyxanthosine ( 17 ).