The crystals of most proteins or other biological macromolecules are poorly ordered and diffract to lower resolutions than those observed for most crystals of simple organic and inorganic compounds. Crystallization in the microgravity environment of space may improve crystal quality by eliminating convection effects near growing crystal surfaces. A series of 11 different protein crystal growth experiments was performed on U.S. space shuttle flight STS-26 in September 1988. The microgravity-grown crystals of γ-interferon D 1 , porcine elastase, and isocitrate lyase are larger, display more uniform morphologies, and yield diffraction data to significantly higher resolutions than the best crystals of these proteins grown on Earth.

Uracil was prepared enriched at C2 with carbon-13 and converted into uridine from which 2,5′-anhydro-1-β-D-ribo-furanosyl and 2,2′-anhydro-1-β-D-arabino-furanosyl uracil were prepared. The 13C2 to vicinal proton coupling constants for these compounds were measured and are compared in terms of the expected torsion angles defined by the two atoms. The evidence suggests the existence of a Karplus-type relationship as is found for vicinal proton coupling. The data establish the anti conformation for uridine in solution.

Reduction of isopropyl tri-0-acetyl-cc-D-arabino-hexopyranosuloside with sodium borohydride or diborane leads almost exclusively to the gluco-configuration. Catalytic reductions, on the other hand, provide an epimeric mixture with the manno-configuration predominating in ratios of about 2:l. The reduction of isopropyl tri-0-acetyl-g-D-lyxo-l~exopyranosuloside with either sodium borohydride or diborane is less stereoselective than in the case of the arabino-isomer and leads to compounds of the galacto-and talo-configurations in the ratio of 3:2. The latter is formed highly stereoselectively when the lyxosuloside derivative is hydrogenated catalytically.2-0-(a-D-Mannopyranosy1)-glycerol and the gluco-isomer are synthesized.La reduction de I'isopropyl tri-0-acityl-3-D-arabino-hexopyranosuloside par le borohydrure de sodium ou le diborane conduit presqu'exclusivement a la configuration g1~~c.o. Les reductions catalytiques donnent d'autre part, un melange d'epimeres avec la configuration manno predominante dans des rapports de 2:l environ. La reduction de I'isopropyl tri-0-acetyl-2-D-lj~xo-hexopyranosuloside soit avec le borohydrure de sodium soit avec le diborane est moins stereoselective que dans le cas de I'isomere arabino et conduit aux composes de configuration galacto et talo dans le rapport 3:2. Ce dernier est form6 de fagon hautement stereoselective lorsque le derive lyxosuloside est hydrogent catalytiquement.Le 27 (1973) In apreviouspublication (I), wereportedthefacile deoxiniations of isopropyl tri-0-acetyl-2-oximino-r-D-arabino-hexopyranoside and its lyxoisomer to the corresponding keto-sugars 1 and 2, respectively, which were characterized as crystalline compounds. Red~lctions of these ulosides to glycosides under a variety of conditions have now been examined. The promise of this approach for the synthesis of a-glucoppranosides was reported in a preliminary communication (2) where it was shown that the reduction of crude isopropyl tri-0-acetyl-r-D-arabino-hexopyranosuloside (1) by sodium borohydride followed by 0-acetylation led to isopropyl tetra-0-acetyl-a-D-glucopyranoside in an overall yield of 80% from the oxime precursor.The purpose of this paper is to report details of this work and to extend the method to preparations of r-D-mannopyranosides, a-D-galactopyranosides, and a-D-talopyranosides.As previously reported (2, 3), reduction of 1 with sodium borohydride gave isopropyl a-D-

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