A-D-Mannoside

Structure and Reactivity of Anhydro-sugars. Part I. Branched-chain Sugars. Part I. Action of Di-ethylmagnesium on Methyl 2 3-Anhydro-4 6-0-benzylidene-a-D-mannoside, A. B. Foster, W. G. Overend, M. Stacey, and G. Vaughan,/. Chem. Soc., (1953) 3308-3313. 

Carbon atom D-Gulose Me a-D-guIoside D-Mannose Me a-D-mannoside... 

The methyl 2,3,4-trimethyl-a-D-mannuronoside (XLI) was synthesized from methyl 2,3,4-trimethyl-a-D-mannoside by the method pre-... 

Three routes to the synthesis of D-mannuronic acid (XLIII) are now known. The first42 was based on the original method of Fischer and Piloty48 and involved the reduction of D-mannosaccharodilactone (XLII) with sodium amalgam. The second44 utilized methyl 2,3-isopropyli-dene-a-D-mannoside (XLIV) which was oxidized at C6 with alkaline potassium permanganate to methyl isopropylidene-a-D-mannuronoside ... 

T. K. Lindhorst, S. Kotter, U. Krallmann-Wenzel, and S. Ehlers, Trivalent a-D-mannoside clusters as inhibitors of type-1 fimbriae-mediated adhesion of Escherichia coli Structural variation and biotinylation, J. Chem. Soc. Perkin Trans., 1 (2001) 823-831. 

Shortly after the above work appeared, Bolliger and Prins90 reported a similar synthesis leading to a 3- rather than a 2-desoxy derivative. Methyl 2,3-anhydro-4,6-benzylidene-a-D-mannoside (LXIV), upon treatment with sodium thiomethoxide, was converted into methyl 3-methyl-thio-4,6-benzylidene-a-D-altroside (LXV) which, after desulfurization and rebenzylidenation, gave methyl 3-desoxy-4,6-benzylidene-a-D-man-noside (LXVI). Methylation of LXV with methyl iodide and silver oxide followed by desulfurization gave methyl 2-methyl-3-desoxy-4,6-benzylidene-a-D-mannoside in poor yield. 

Results are expressed as fig of p-nitrophenol liberated per g of seed from 6 mM p-nitrophenyl a-D-mannoside in 1 hr at 37° and pH 5. Coarsely ground beans. Defatted sweet-almond meal. A commercial /3-D-glucosidase preparation purified from emulsin. a-D-Mannosidase activity is given per g of purified material. 

Results are expressed as /ag of p-nitrophenol liberated per g of moist tissue from p-nitrophenyl a-D-mannoside in 1 hr at 37° under the conditions stated. 

Results are expressed as percentages of the activity of the whole sucrose homogenate. All assays were done in the presence of Triton X-100, with p-nitrophenyl a-D-mannoside as substrate. Fractions I, nuclei and unbroken cells II, mostly mitochondria III, mostly microsomes and IV, final supernatant liquor. 

One unit of a-D-mannosidase liberates 1 /xg of p-nitrophenol from 6 mM p-nitro-phenyl a-D-mannoside in 1 hr at 37° and pH 5. Protein was determined by the method of Lowry and coworkers,59 with bovine albumin as the standard. Zn2+ was added to the preparation after Stage 3. 

Fig. 1.—Hydrolysis at Different pH Values, in Acetate Buffer, of 6 inM p-Nitrophenyl a-D-Mannoside by Limpet a-D-Mannosidase.4S [A, no addition in the presence of A, 0.1 mM ZnS04 O, 0.1 M NaCl, and , 0.1 M NaCl + 0.1 mM ZnS04. The a-D-man-nosidase activity is expressed as a percentage of the maximum value obtained in the presence of Zn2+ and Cl-.]...

Fig. 2.—Effect of Concentration of Substrate on the Rate of Hydrolysis4 of p-Nitro-phenyl a-D-Mannoside in Acetate Buffer, pH 3.5, at 37° by a Crude Preparation of Limpet a-D-Mannosidase in the Presence of , 0.1 mM ZnS04 and 0.1 M NaCl A, 0.1 M NaCl only and O, 0.1 mM ZnS04 only.

Glycoproteins or glycopeptides are frequently treated with a-D-mannosidases (a-D-mannoside mannohydrolases, E.C. 3.2.1.24) D-mannose is often released (see Table XIV). Prior treatment with other enzymes is often found necessary (see items 5 and 6). 

From methyl-a-D-mannoside a similar product, C7H,0O2(ON02)4, was obtained in the form of needles, melting at 36°C, rather unstable at 50°C. 

An intermediate in Hudson s synthesis4 of D-rhamnose (24) is methyl 2,3,4-tri-0-benzoyl-6-deoxy-a-D-mannoside (25). Frequently, direct replacement of the methoxyl group at C-l of O-acylated hexopyranosides by halide proceeds with difficulty (or not at all) however, treatment of (25) with hydrogen bromide in acetic acid resulted in the slow replacement of the methoxyl group by bromide ion, to give the desired 2,3,4-tri-O-... 

O-p-tolylsulfonyl-a-D-mannoside (39) in 37% yield. Treatment of (39) with sodium iodide in acetone gave the 6-iodo derivative (40), which underwent reduction with hydrogen in the presence of a nickel boride" catalyst" to give methyl 4-0-benzoyl-2,3-0 carbonyl-6-deoxy-o>-D-manno-side (41) in 95% yield. Reaction of (41) with hydrogen bromide in acetic acid effected replacement of the methoxyl group at C-l, affording crystalline... 

---