Reduction of α-D-Hexopyranosulosides

Abstract

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-

The azidonitration of tri-O-acetyl-D-galactal

“…The preparation of a-D-galactosaminides by way of 2-oximo-a-D-lyxo-hexopyranosides (17) provided the first synthesis of an N-acetyl-a-D-galactosaminidic disaccharide (18). However, to date, this method is handicapped by the fact that reduction of the intermediate oxime to the galacto configuration cannot be achieved with a high degree of stereoselectivity.…”

Measurement of endo-α-mannosidase activity using a fluorescently labeled oligosaccharide derivative

“…Having obtained the mannotetraose derivative 18 possessing a C-2 free hydroxyl group at the non-reducing end of the mannose residue, we converted the stereochemistry at the C-2 hydroxyl group to the gluco configuration using an oxidation-reduction method. 12,13) The treatment of compound 18 with DMSO and Ac 2 O gave ulosyl derivative 19. The product was reduced by sodium triacetoxyborohydride (NaBH(OAc) 3 ) to give glucoderivative 20 (yield, 63%) as a major product.…”

Syntheses of derivatives of N-acetyl-D-lactosamine from D-lactal hexaacetate. Hexa-O-acetyl-2-deoxy-2-phthalimido-β-D-lactosyl chloride

“…We now wish to report details for the preparation of 7 from D-lactal hexaacetate (I) by two different routes. One process is based on the procedure for the preparation of 2-amino-2-deoxyci-glycopyranoside which was developed in this laboratory (8) and which will be termed the nitrosochloride route. The other process for the preparation of 7 is based on the azidonitration of glycals (9,10) to form 2-azido-2-deoxy glycopyranosides and which will be designated as the azidonitrate route.…”