THE CONFIGURATION AND CONFORMATION OF DI-D-FRUCTOSE ANHYDRIDE .1. THECRYSTAL-STRUCTURE AND MOLECULAR-STRUCTURE OF RA-O-ACETYL-6,6'-DI(TRIPHENYLMETHYL)-DI-D-FRUCTOSE ANHYDRIDE-I

The crystal structure of ra-O-acetyl-6,6'-di(triphenylmethyl)-di-D-fru ctose anhydride I (1) has been determined by single-crystal X-ray diff raction. The crystals are monoclinic, space group P2(1) with a = 16.39 9(2), b = 9.091(2), c = 17.946(4) Angstrom, beta = 103.66(1)degrees, V = 2600(2) Angstrom(3), and Z = 2. The structure was refined to R = 0. 044 and R(W) = 0.051 for 4403 observed reflections. The structure anal ysis of 1 showed that the previously assigned chemical structure of di -D-fructose anhydride I is undoubtedly alpha-D-fructofuranose beta-D-f ructofuranose 1,2':2,1'-dianhydride. The conformations of the furanose rings are E(5) with P = 59.8 and tau(m) = 43.2 degrees for D-fructose 1, and T-2(3) With P = -34.39 degrees and tau(m) = 39.64 degrees for D-fructose 2. The two furanose fragments are linked by a 1,4-dioxane r ing in a spiro arrangement. The 1,4-dioxane ring has a chair conformat ion with Cremer-Pople puckering parameters Q = 0.527 Angstrom, phi = 7 2.2 degrees and theta = 14.2 degrees.