STRUCTURES OF THE 2',3'-DIDEOXY AND 2',3'-DIDEHYDRO-2',3'-DIDEOXY ANALOGS OF TIAZOFURIN

2',3'-Dideoxytiazofurin [2-(2',3'-dideoxy-beta-D-glycero-pentafuranosyl)thiazole-4-carboxamide] hemihydrate (1), C9H12N2O3S.1/2H2O, M(r) = 237.3, monoclinic, C2 a = 23.141 (2), b = 5.912 (1), c = 8.252 (1) angstrom, beta = 90.71 (1)-degrees, V = 1128.9 (4) angstrom 3, Z = 4, D(x) = 1.396 g cm-3, Cu K-alpha, lambda = 1.54178 angstrom, mu = 25.0 cm-1, F(000) = 500, T = 295 K, R = 0.0319 for all 1316 unique reflections. 2',3'-Didehydro-2',3'-dideoxytiazofurin [2-(2',3'-dideoxy-beta-D-glycero-pent-2-enofuranosyl)thiazole-4-carboxamide] (2), C9H10N2O3S, M(r) = 226.3, orthorhombic, P2(1)2(1)2(1), a = 22.172 (2), b = 8.019 (1), c = 5.991 (1) angstrom, V = 1065.2 (4) angstrom 3, Z = 4, D(x) = 1.411 g cm-3, Cu K-alpha, lambda = 1.54178 angstrom, mu = 25.9 cm-1, F(000) = 472, T = 295 K, R = 0.0344 for all 957 unique reflections. Both structures show a close contact between the thiazole S and the pentose O(1') atoms. S...O(1') distances are 2.834 (2) angstrom in (1) and 2.835 (1) angstrom in (2), resulting from C-glycosidic torsion angeles of 14.1 (2) and 5.2 (3)-degrees respectively. This unusual feature is conserved in the crystal structures of other thiazole nucleosides [Goldstein, Mao & Marquez (1988). J. Med. Chem. 31, 1026-1031].