Mannopyranosides preparation

In 1938, Lake and Peat168 reported that methyl 2,3-anhydro-4,6-dimethyl-/3-D-mannopyranoside (prepared from methyl 2-tosyl-3,4,6-triacetyl- S-D-glucopyranoside by detosylation with sodium methoxide and subsequent methylation)164 gave rise, when boiled with sodium methoxide in methyl alcohol, to almost equal proportions of methyl... 

Methylation (methyl iodide-silver oxide) of methyl 3-0-benzyl-4,6-0-benzyl-idene-a-D-mannopyranoside (prepared by selective benzylation of the equatorial hydroxy-group of methyl 4,6-O-benzyhdene-a-D-mannopyranoside) followed by hydrogenolysis and hydrolysis with acid has provided a convenient synthesis of 2-0-methyl-D-mannose. 3-O-Methyl- and 3,6-di-O-methyl-D-galactose have been synthesized by straightforward procedures from methyl P-D-galactopyrano-... 

A mixture of d- and l- hexoses also results from the hydroboration of these 5-enes. Hydroboration results in anti-Markownikoff, cw-hydration of the double bond and the amount of each hexose formed varies according to the nature of the substituent groups. For example, hydroboration (23) of methyl 6-deoxy-a-D-ryZo-hex-5-enopyranose (3) affords methyl a-D-glucopyranoside and methyl / -L-idopyranoside in the ratio of 1 2.5 respectively whereas hydroboration of the fris-trimethylsilyl ether of 3 afforded them in the ratio 1 0.6 respectively. The hydroboration method can be used to achieve specific labelling of hexoses with tritium methyl-/ -L-idopyranoside[5-H3] and methyl a-D-glucopyranoside [5-H3] were thus prepared (23). Similarly, hydroboration of the D-Zt/ro-hex-5-eno derivative (14) with diborane-H3 followed by removal of the isopropyli-dene group, afforded methyl a-D-mannopyranoside [5-H3] and methyl / -L-gulopyranoside [5-H3] in the ratio of 1 2 respectively (23). 

As part of a study on cell-surface glycans, 2,3-bis(tetradecyloxy)propyl 2-deoxy-2-fluoro-a- and - -D-mannopyranosides were prepared by condensation of 3,4,6-tri-0-benzyl-2-deoxy-2-fluoro-a-D-mannopyranosyl chloride with 2,3-bis(tetradecyloxy)propanol. 

Zervas48 through the catalytic reduction of 2,3,4,6-tetraacetyl-2-hydroxy-D-glucal, has recently been prepared by the reductive desulfurization of ethyl tetraacetyl-l-thio-/ -D-mannopyranoside (XL),47 a substance which has been obtained through the mercaptolysis of mannosidostreptomycin48 and may be prepared through the prolonged action of ethyl mercaptan and hydrochloric acid on D-mannose. 

Example 19 Crich and Dudkin have used phosphoroamidite containing two different protecting groups 0-benzyl-0-2-cyanoethyl-iV,Ar-diisopropyl-phosphoroamidite [48]. This phosphitylating reagent was prepared in excellent yield from 2-cyanoethyl NyN diisopropylchlorophosphoroamidite, which was immediately used for coupling with an appropriate alcohol in the presence of tetrazole and oxidized without delay with TBHP. This kind of phosphorylation procedure was used in the synthesis of 4,8,12,16,20-pen-tamethyl-pentacosylphosphoryl / -o-mannopyranoside, an unusual / -man-nosyl phosphoisoprenoid from Mycobacterium avium. 

A. C. Richardson, An improved preparation of methyl 3-amino-3-deoxy-a-D-mannopyranoside hydrochloride, J. Chem. Soc. (1962) 373-374. 

Dialkyl methyl phosphonate derivatives 37a-c of mannopyranosides may be prepared from cyclic sulfate 36 by reaction with the appropriate lithiated methylphosphonate, prepared by titration of the corresponding methyl-phosphonate with butyllithium in the presence of 1,1-diphenylethylene as indicator (Equation 4) <2002TL4017>. 

For the assay of a-D-mannosidase, the incubation mixture employed in our laboratory contained 0.5 ml of M acetate buffer at a pH appropriate for the particular enzyme preparation, 1.5 ml of 16 mM p-nitrophenyl a-D-mannopyranoside, 1.5 ml of water (which could be replaced by other additives as required), and 0.5 ml of suitably diluted, enzyme preparation. After 1 hour at 37°, the reaction was terminated, and the color was developed by adding 4 ml of 0.4 M glycine-sodium hydroxide buffer, pH 10.5. The mixture was centrifuged for 15 minutes at 1500 g, and the color intensity of the liberated p-nitrophenol (25-150 fig) in the supernatant liquor was measured on a Spekker photoelectric absorptiometer, with use of Ilford No. 601 violet filters having maximal transmission at 430 nm, and a 1-cm light path. Separate control-experiments for enzyme and sub-... 

As discussed under Purification and pH and Stability [see Sections 11,4 (p. 409) and 11,6 (p. 413)], a-D-mannosidase is unstable at low pH values unless Zn2+ is added. In the following experiments employing a partially purified, jack-bean meal preparation (see Table V, stage 3 p. 410) to which Zn2+ had not been added, the enzyme was pre-incubated at 37° and pH 5 before assay at the same pH with p-nitrophenyl a-D-mannopyranoside as the sub-... 

Several 0-aminoacyl sugars were prepared to study a relationship between taste and chemical structure. Methyl a-D-glucopyranoside, methyl a-D-galactopyranoside and methyl a-D-mannopyranoside were selected as sugar skeletons. As basic amino acids, esters of lysine, ornithine, a,Y-diaminobutyric acid, and a,p-diaminopropionic acid were introduced into 2-0-, 3-0-, and 4-0- positions of sugars leaving only 6-hydroxyl group free. The results of sensory analysis are list in Table VI. O-... 

The paradigmatic hexosaminidase inhibitor with basic nitrogen in the ring, 2-acetamido-1,2-dideoxynojirimycin (2-acetamido-l,2,5-trideoxy- 1,5-imino-D-glucitol, 33) has not been found naturally to date. This inhibitor was first prepared by Fleet and co-workers [76,77] in a 17-step synthesis from D-glucose via methyl 3-0-benzyl-2,6-dideoxy-2,6-imino-a-D-mannopyranoside together... 

Watters, Hockett and Hudson1 have prepared a non-crystalline monomethylmannose which forms an osazone with the same properties as those of 6-methyl-n-glucosazone. The synthesis was achieved by methylation of methyl 2,3,4-triacetyl-a-D-mannopyranoside, followed by hydrolysis. Schmidt and Heiss,13 studying the epimerization of 6-methyl-D-gluconic acid, have claimed to have isolated the phenyl-hydrazide of 6-methyl-n-mannonic acid. 

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