THE CRYSTAL AND MOLECULAR-STRUCTURES OF 4-CYANOPHENYL 1,5-DITHIO-BETA-D-XYLOPYRANOSIDE S-5 OXIDE AND 4-ETHYL-2-OXO-2H-1-BENZOPYRAN-7-YL 5-THIO-BETA-D-XYLOPYRANOSIDE S-5 OXIDE

Crystals of 4-cyanophenyl 1,5-dithio-beta-D-xylopyranoside S-5 oxide ( 1) and 4-ethyl-2-oxo-2H-1-benzopyran-7-yl 5-thio-beta-D-xylopyranoside S-5 oxide (2) are monoclinic, space group P2(1), with two independent thioxylosides molecules in the asymmetric unit. The unit cell dimensi ons are a=26.385, b=5.934, c=8.902 Angstrom, and beta=109.90 degrees f or I and a=16.033, b=16.676, c=6.459 Angstrom, and beta=91.26 degrees for 2. The present work provides structural information on the influen ce of substitution of intracyclic and glycosidic oxygen atoms by sulfu r atoms, as well as on the influence of aromatic rings and of sulfoxid e groups on the carbohydrate moiety. In both molecules, the xylopyrano sides rings have the classical C-4(1) conformation. For 1, the orienta tion of the phenyl substituent with respect to the xylopyranose is ver y similar in the two independent molecules: the Phi and Psi torsion an gles are respectively: (-99.5 degrees, 153.8 degrees) and(-102.1 degre es, 154.2 degrees). This is not the case for 2, for which these values are strikingly different: (-79.4 degrees, 172.1 degrees) and (-130.2 degrees, -178.4 degrees). In each structure, the molecules are hydroge n bonded within a network of infinite chains. (C) 1997 Elsevier Scienc e Ltd.