The DNA-stabilising nucleoside 7-iodo-2'-deoxytubercidin: Its structure in the solid state and in solution

The crystal structure of 7-iodo-2'-deoxytubercidin 2 has been determined and was compared with those of 2'-deoxytubercidin 3 and 2'-deoxyadenosine 4, The bulky 7-iodo substituent lies 13.2 pm below and the nitrogen of the 6-amino group 5.5 pm above the 7-deazapurine plane, The puckering of compound 2 is (3).E while compound 3 shows a T-2'(3') sugar pucker. The conformation in aqueous solution, determined by H-1 NMR spectroscopy, is only slightly different, showing a (2')E conformation, The glycosylic bond torsion angle is anti in all cases.