Galactopyranoside methyl 4,6-dichloro-4,6-dideoxy

C7H12C1204 Methyl 4,6-dichloro-4,6-dideoxy-a-D-galactopyranoside MCDGAL 31 366... 

Reactivity at 0-3, in addition to that at 0-4 and 0-6, was observed with methyl )3-D-galactopyranoside, which, when treated with sulfuryl chloride, yielded methyl 3,4,6-trichloro-3,4,6-trideoxy-/J-D-allopyranoside 2-(chlorosulfate) in 56% yield.352 In contrast, under similar conditions, methyl a-D-galactopyranoside gave352 methyl 4,6-dichloro-4,6-dideoxy-a-D-glucopyranoside 2,3-di(chlorosulfate). Further examples of the dependence of the reactivity on the configuration of C-l are the conversion of methyl 4,6-0-benzylidene-/3-D-glucopyranoside into methyl 4,6-0-benzylidene-3-chloro-3-deoxy-/3-i>allopyranoside by sulfuryl chloride,352 and of methyl 4,6-0-benzylidene-a-D-glucopyranoside, under similar conditions, into the 2,3-di(chlorosulfate).355... 

The reaction of sulfuryl chloride with carbohydrates to give chloro-deoxy derivatives has been reviewed briefly in this Series.98 The reaction of sulfuryl chloride with monosaccharides has been shown to afford products in which the secondary hydroxyl groups are replaced by chlorine with inversion of configuration.68-75 Jones and coworkers reported that the reaction of methyl a-D-glucopyranoside with sulfuryl chloride and pyridine in chloroform at room temperature proceeds by way of the 4,6-bis(chlorosulfate) by an Sn2 process, with chloride as the nucleophile, to give methyl 4,6-dichloro-4,6-dideoxy-a-D-galactopyranoside 2,3-bis(chlorosulfate).74... 

It has been found32 that treatment of methyl 4,6-dichloro-4,6-dideoxy-a-D-gaIac-topyranoside 2,3-di(chlorosulfate) (8) with sodium bromide in N,N-dimethyl-formamide at room temperature affords methyl 4,6-dichloro-4,6-dideoxy-o -D-galactopyranoside and its 2- and 3-mono(chlorosulfate) derivatives. These three products were also formed, in addition to a mono(azidosulfate) derivative, when 8 was treated with sodium azide in N,N-dimethylformamide at room temperature. 

An X-ray crystallographic analysis has been performed44 on methyl 4,6-dichloro-4,6-dideoxy-a-D-galactopyranoside prepared by way of reaction of methyl a-D-glucopyranoside with sulfuryl chloride the molecule has the Cl (d) conformation, and the bond distances and valency angles are similar to those in simple sugars. 

In 1921 Helferich [34J found that treatment of methyl a-D-glucopyranoside 18 with sulfuryl chloride in a mixture of pyridine and chloroform at 5°C afforded a compound, the structure of which was established several years later [37,38] to be that of methyl 4,6-dichloro-4,6-dideoxy-a-D-galactopyranoside 2,3-cyclic sulfate (19 Scheme 3). The cyclic sulfates are readily cleaved by dilute alkalis, or by methanolic ammonia, to give the salt of a monosulfate the hemi-ester is then desulfated by acid to yield the chlorodeoxy sugar [35,36]. Both of these reactions occur with retention of configuration [37]. 

Methyl a-D-glucopyranoside (18, 40 g) was converted into methyl 4,6-dichloro-4,6-dideoxy-a-D-galactopyranoside 2,3-di(chlorosulfate) (20,78 g), by the method of Jennings. and Jones [39,40]. The syrupy material was dissolved in methanol (1200 mL), and a golution of sodium iodide [63 g in 160 mL of methanol-water (1 1, v/v)] was added. The gQlgtion was neutralized with sodium hydrogen carbonate. The insoluble material was SSHoSed by filtration, and the filtrate was concentrated to dryness. The residue was... 

A solution of methyl 4,6-dichloro-4,6-dideoxy-a-D-galactopyranoside [28] (37, 1 g) in absolute ethanol (30 mL) containing triethylamine (1.3 mL) and W-4 Raney nickel catalyst... 

A stirred mixture of methyl 2,3-di-0-acetyl-4,6-dichloro-4,6-dideoxy-a-D-galactopyrano-side (41, 1 mmol) [prepared by acetylation (acetic anhydride-pyridine) of methyl 4,6-dichloro-4,6-dideoxy-a-D-galactopyranoside 37], sodium azide (4 mmol), and dry N,N-... 

Chalcose (4,6-dideoxy-3-0-methyl-D-xy/o-hexose, 152) was obtained from methyl 4,6-dichloro-4,6-dideoxy-a-D-galactopyranoside (164).240 The dichloride 164 was readily prepared by selective chlorination of methyl ot-D-glucopyranoside with... 

Reaction of Methyl 4,6-Dichloro-4,6-dideoxy-a-D-galactopyranoside 2,3-Di(chloro-sulfate) with Sodium Azide, and with Sodium Bromide, in A/,2V-Dimethylformamide, H. Parolis, W. A. Szarek, and J. K. N. Jones, Carbohydr. Res., 19 (1975) 97-105. 

The reduction of chlorodeoxy sugars has been achieved [31,32] in high yield by means of tributyltin hydride in the presence of 2,2 -azobis(2-methylpropionitrile). The reaction with methyl 2,3-di-0-acetyl-4,6-dichloro-4,6-dideoxy-a-D-galactopyranoside at 60°C gave [31] methyl 2,3-di-0-acetyl-6-chloro-4,6-dideoxy-ot-D-xylo-hexopyranoside as the main product. A free-radical mechanism has been proposed [33] for the reduction of alkyl halides by organotin hydrides. In accordance with this proposal, the presence of the radical initiator 2,2 -azobis(2-methylpropionitrile) was essential for the reduction of chlorodeoxy sugars moreover, the relative reactivities of the two chlorine atoms in methyl 2,3-di-0-acetyl-4,6-dichloro-4,6-dideoxy-a-D-galactopyranoside follow a free-radical order. 

It is also well known that sweet and bitter tastes interact. It is the case for the inhibition of sucrose sweet taste by inhibitors like lactisol or methyl-4, 6-dichloro-4,6-dideoxy-galactopyranoside which was attributed to their hydrophobic character and their bitterness (Mathlouthi et al., 1993). Bitter taste was foimd to be suppressed by sweeteners such as sucrose (Bartoshuk, 1975). The masking of unpleasant taste by pleasant (sweet) stimuli is greatly sought after in pharmaceuticals. For example, cyclodextrins were described to have the ability of masking the bitterness of drugs like propantheline... 

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