STRUCTURES OF THE 4-CYANO AND 4-METHYLAMIDATE ANALOGS OF TIAZOFURIN

4-Cyanotiazofurin [2-(beta-D-ribofuranosyl)thiazole-4-carbonitrile, (1)], C9H10N2O4S, M(r) = 242.3, monoclinic, P2(1), a = 7.329 (1), b = 8.295 (1), c = 8.697 (1) angstrom, beta = 90.90 (1)-degrees, V = 528.7 (1) angstrom3, Z = 2, D(x) = 1.52 g cm-3, Cu Kalpha, lambda = 1.54178 angstrom, mu = 27.2 cm 1, F(000) = 252, T = 293 K, R = 0.0487 for all 1171 unique reflections. 4-Methylamidatetiazofurin [methyl 2-(beta-D-ribofuranosyl)thiazole-4-carboximidate, (2)], C10H14N2O5S, M(r) = 274.3, orthorhombic, P2(1)2(1)2(1) a = 8.596 (1), b = 11.060 (1), c = 26.064 (1) angstrom, V = 2478.1 (2) angstrom3, Z = 8, D(x) = 1.47 g cm-3 Cu Kalpha, angstrom = 1.54178 angstrom, mu = 24.5 cm-1, F(000) = 1152, T = 293 K, R = 0.0374 for all 2902 unique reflections. Compound (2) crystallizes with two crystallographic unique structures in the asymmetric unit [(2a) and (2b)]. All three structures show a close contact between the thiazole sulfur and the pentose oxygen O(1'). S...O(1') distances are 2.936 (3) angstrom in (1), 2.773 (2) angstrom in (2a) and 2.878 (2) angstrom in (2b), resulting from C-glycosidic torsion angles of 34.5 (4), 15.6 (3) and 27.2 (3) respectively. This interesting feature is conserved in the crystal structures of other thiazole nucleosides [Burling & Goldstein (1992). J. Am. Chem. Soc. 114, 2313-2320].