Carbohydrates selective chlorination

R. S. Bhatt, L. Hough, and A. C. Richardson, Selective chlorination of methyl p-lactoside with mesyl chloride in DMF, Carbohydr. Res., 49 (1976) 103-118. 

The selective replacement of hydroxyl groups in carbohydrates by chlorine has been achieved by the use of sulfuryl chloride.1,74,87,88 The reaction of sulfuryl chloride with maltose89,90 and methyl /3-maltoside24 has been studied. Treatment of maltose with sulfuryl chloride, initially for 2 h at — 70° and then processing at room temperature, gave, after methyl glycosidation and dechlorosulfation, a low yield... 

Chlorination. Methanesulfonyl chloride can effect the direct chlorination of various substrates. The most notable of these reactions is the selective chlorination of the C-6 primary hydroxy group of carbohydrates (eq 2). Under these conditions, 2-furyl alcohol (eq 3) and guanine V-oxide (eq 4) can also be chlorinated directly. 

The aromatic nature of lignin contrasts with the aliphatic stmcture of the carbohydrates and permits the selective use of electrophilic substitution reactions, eg, chlorination, sulfonation, or nitration. A portion of the phenoUc hydroxyl units, which are estimated to comprise 30 wt % of softwood lignin, are unsubstituted. In alkaline systems the ionized hydroxyl group is highly susceptible to oxidative reactions. 

OH — X. Pi. carbohydrate hydroxyl group can be replaced by halogen (bromine, chlorine, iodine) by treatment in DMF with 2 eq. each of triphenylphosphine and an N-halosuccinimidc. The by-products are succinimide and triphenylphosphine oxide. Yields are generally high. Primary hydroxyl groups can be selectively replaced in the presence of secondary hydroxyl groups. 

Carbohydrates. Mild oxidants such as chlorine, bromine, or iodine readily convert the aldehyde end groups in the wood polysaccharides to aldonic acid end groups. Nitrogen dioxide selectively converts the primary hydroxyl groups on C-6 in cellulose to carboxyl groups (J3). Periodic acid is a specific oxidant for vicinal diols and yields formaldehyde from primary hydroxyl groups and aldehydes from secondary. 

The characterization of water-soluble components in slurries is one use of SPME with mixed solid-liquid samples. In one application, dried homogenized solid samples (10 mg of sewage sludge or sediment) were slurried in 4 ml of H,0 saturated with NaCl and adjusted to pH 2 with HCl for extraction for 1-15 h, which was followed by desorption into 4 1 methanol/ethanol over 2 min. The extracted compounds were either injected into a liquid chromatograph or fed directly via an electrospray ionization interface to a mass spectrometer with 1 s miz scans from 50-700 or selected-ion monitoring. The major components extracted included phthalates, fatty acids, non-ionic surfactants, chlorinated phenols and carbohydrate derivatives [235]. 

There is increasing interest in the use of oxone (Z) for bleaching and bleach sequences such as OZEP have been examined experimentally (P stage is peroxide). It is likely that the use of oxygen and ozone in combination will be used over the next decade, with ozone replacing part or all of the chlorine. One of the disadvantages of ozone is its lack of selectivity and its tendency to attack carbohydrates as well as lignin. 

Metallurgical, materials, ceramic and chemical engineers worldwide will welcome this new compilation of thermochemical data by Professor Barin. Here they will find the most comprehensive tables yet available for the thermodynamic properties of pure substances as a function of temperature at 100° intervals. Almost twenty-four hundred substances are included - the elements, and compounds of two, three, and four elements. The vast majority of substances are inorganic, but Dr. Barin has included a generous selection of the more common hydrocarbons, carbohydrates, and a few chlorinated hydrocarbons. The format of the tables conforms to that of the JANAF tables, and SI units are employed. 

Montforts et further explored this approach by attaching hydrophilic carbohydrate structural units to certain chlorins (e.g., 406). Such conjugation increased the water solubility of the parent chlorins 407 and 408. By introducing an estradiol with a diethyl spacer, the chlorin-estrogen conjugate was then prepared in the hope that it would bind to an estrogen receptor which could induce selective destruction of mammalian carcinoma (Scheme 82). 

Selective acylation occurs at C-6 of methyl e<-D-glucopyranoside on treatment with hexachloro- or pentachloro-propanone to yield tri-chloro- or dichloro-acetates respectively. The chlorinated ester group is easily removed by ammonia in ether and thus constitutes a base-labile complement to the acid-labile trityl function (Scheme 3). Trifluoroacetylation of carbohydrates for g.c. analysis has... 

Sucralose (also called 4,T,6 -trichloro-4,T,6 -trideoxygalactosucrose, E955) is technically a chlorinated carbohydrate, and it is made by selectively replacing three hydroxyl groups on the sugar molecule with three chlorine atoms (Figure 4A.35). 

The ability of the custom-built dual gate/ion mobility quadrupole ion trap mass spectrometer equipped with electrospray ionization (ESI-DG-IM-QIT-MS) to perform mobility-filtered ion selection prior to mass analysis has been evaluated with peptides in the positive ion mode and carbohydrates in the negative ion mode. The separation of a disaccharide melibiose [a-D-Gal-(l-6)-D-Glc] and a trisaccharide rafflnose [a-D-Gal-(l-6)-a-D-Glc-(l-2)-P-D-Fru] as chlorine adducts in the negative... 

The mass spectra of TMS derivatives of nucleosides selectively labelled with deuterium and oxygen-18 have been recorded.The position of chlorine atoms in the carbohydrate ring of chloro-deoxy-nucleosides can be established from their mass spectrum. 

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