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'-deoxyur idine (III) have been obtained from data collected on a four-circle En raf-Nonius diffractometer (CAD-4 system). Space group, unit/cell param eters 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%; I I, monoclinic, P2(1), a = 8.720(4), b = 20.793(4), c = 7.884(4) Angstr om, beta = 95.06(2)degrees, R = 5.8%; III, monoclinic, p2(1), a = 9.26 0(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 wi th those of 5-(5-chlorothien-2-yl)-2'-deoxyuridine (IV) previously rep orted in order to explain their affinity for HSV-1 thymidine kinase an d their eventual interaction with viral DNA polymerase. The main struc tural features observed are the coplanarity of the uracil and thienyl cycles stabilized by a S-O intramolecular interaction and the formatio n of dimeric intermolecular H bonds between two uracil moieties.