title: The regioisomeric 1H(2H)-pyrazolo[3,4-d]pyrimidine N1- and N2-(2'-deoxy-beta-D-ribofuranosides).
abstract: In the title regioisomeric nucleosides, alternatively called 1-(2-deoxy-beta-D-erythro-furanosyl)-1H-pyrazolo[3,4-d]pyrimidine, C(10)H(12)N(4)O(3), (II), and 2-(2-deoxy-beta-D-erythro-furanosyl)-2H-pyrazolo[3,4-d]pyrimidine, C(10)H(12)N(4)O(3), (III), the conformations of the glycosylic bonds are anti [-100.4 (2) degrees for (II) and 15.0 (2) degrees for (III)]. Both nucleosides adopt an S-type sugar pucker, which is C2'-endo-C3'-exo ((2)T(3)) for (II) and 3'-exo (between (3)E and (4)T(3)) for (III).