5-(thien-2-yl) uracil analogs: 5-(5-methylthien-2-yl)-2'-deoxyuridine, 5-(5-thien-2-yl)-2'-deoxyuridine, and 5-(5-bromothien-2-yl)-2'-deoxyuridine

Crystal structures of 5-(5-methylthien-2-yl)-2'-deoxyuridine (I), 5-(5-thien-2-yl)-2'-deoxyuridine (II) and 5-(5-bromothien-2-yl)-2'-deoxyuridine (III) have been obtained from data collected on a four-circle Enraf-Nonius diffractometer (CAD-4 system). Space group, unit/cell parameters and final R indices are: I, monoclinic, P2(1), a = 9.105(2), b = 20.819(2), c = 7.932(2) Angstrom, beta = 98.79(2)degrees, R = 5.7%; II, monoclinic, P2(1), a = 8.720(4), b = 20.793(4), c = 7.884(4) Angstrom, beta = 95.06(2)degrees, R = 5.8%; III, monoclinic, p2(1), a = 9.260(2), b = 41.655(7), c = 7.926(2) Angstrom, beta = 97.996(13)degrees, R = 9.4%. Structural properties of the title compounds are compared with those of 5-(5-chlorothien-2-yl)-2'-deoxyuridine (IV) previously reported in order to explain their affinity for HSV-1 thymidine kinase and their eventual interaction with viral DNA polymerase. The main structural features observed are the coplanarity of the uracil and thienyl cycles stabilized by a S-O intramolecular interaction and the formation of dimeric intermolecular H bonds between two uracil moieties.