Chlorination of cellulose with methanesulphonyl chloride in N,N dimethylformamide and chloral

Treatment of hardwood dissolving sulphate pulp with N,N-dimethylformamide, chloral, and methanesulphonyl chloride at 75° effective rapid and selective chlorination, initially at the primary positions. When most of the primary hydroxyl groups had been replaced, reaction occurred at HO-3 to give 3,6-dichloro-3,6-dideoxy-D-allose residues. 4,6-Dichloro-4,6-dideoxy-D-galactose residues, derived from non-reducing end-groups were detected only in highly chlorinated cellulose. The degradation of cellulose during chlorination was investigated by gel-permeation chromatography.     

Cellulose esters from waste cotton fabric via conventional and microwave heating

The esterification of cellulose from waste cotton fabric in a N,N-dimethylacetamide/lithium chloride solvent system was carried out using different types of fatty acid chloride including butyryl chloride, capryloyl chloride, and lauroyl chloride as esterifying agents, and N,N-dimethyl 1-4-aminopyridine as a catalyst under conventional and microwave activation. Microwave esterification was performed under 2.45 GHz with power varying from 90 to 450 W. The optimum conditions for esterification of cotton cellulose with various esterifying agents were investigated in terms of reaction time and temperature to attain appropriate %weight increase and degree of substitution of esterified-cellulose. The degree of substitution, functional group and chemical structure, and thermal stability of cellulose ester powder were characterized by ¹H NMR, FTIR, and TGA/SDTA analysis. Morphologies, crystallinity, and solubility of modified cellulose by two different heating methods were compared.     

Facile preparation of deoxy(thiocyanato)celluloses

Deoxy(thiocyanato)celluloses were prepared by treating chlorodeoxycellulose fabrics with potassium thiocyanate in N,N-dimethylformamide. Under optimal reaction-conditions, more than 80% of the chlorine atoms in the cellulose derivative were replaced by thiocyanate groups. Both the chlorodeoxy- and deoxy(thiocyanato)cellulose fabrics exhibited moderate antibacterial activities.Variables studied were thiocyanate concentration, reaction time and temperature, and degree of substitution of the chlorodeoxycellulose in the fabrics being treated. The effect that each of these variables had on the replacement of chlorine atoms by thiocyanate groups was investigated. The tensile, wrinkle-recovery, and biocidal properties of the chlorodeoxy- and deoxy(thiocyanato)cellulose fabrics were also compared.     

Enhancement of enzymatic saccharification of cellulose by cellulose dissolution pretreatments

Attempts were made to enhance cellulose saccharification by cellulase using cellulose dissolution as a pretreatment step. Four cellulose dissolution agents, NaOH/Urea solution, N-methylmorpholine-N-oxide (NMMO), ionic liquid (1-butyl-3-methylimidazolium chloride; [BMIM]Cl) and 85% phosphoric acid were employed to dissolve cotton cellulose. In comparison with conventional cellulose pretreatment processes, the dissolution pretreatments were operated under a milder condition with temperature <130 °C and ambient pressure. The dissolved cellulose was easily regenerated in water. The regenerated celluloses exhibited a significant improvement (about 2.7- to 4.6-fold enhancement) on saccharification rate during 1st h reaction. After 72 h, the saccharification yield ranged from 87% to 96% for the regenerated celluloses while only around 23% could be achieved for the untreated cellulose. Even with high crystallinity, cellulose regenerated from phosphoric acid dissolution achieved the highest saccharification rates and yield probably due to its highest specific surface area and lowest degree of polymerization (DP).     

Polysaccharide sulfates. I. cellulose sulfate with a high degree of substitution

Previous methods for the sulfation of cellulose have a number of disadvantages among which excessive degradation and incomplete substitution are the most common. These disadvantages are overcome if a complex of sulfur trioxide with a neutral, highly polar compound, such as N,N-dimethylformamide, is used as the sulfating agent. For the sulfation of cellulose with this complex, any grade or type of cellulose is suitable. The resulting products usually have degrees of substitution greater than 2. The viscosities of their aqueous solutions are relatively high, indicating that degradation is minor. Two of the most interesting properties of this relatively undegraded cellulose sulfate are its reactivity with proteins and the gelation of its aqueous solutions to form thermoreversible gels in the presence of potassium, rubidium, or cesium ions. The properties are surprisingly similar to those of carrageenan, a polysaccharide sulfate occurring naturally in a number of red marine algae.     

Reverse-phase purification and silica gel thin-layer chromatography of porphyrin carboxylic acids

Thin-layer chromatography on silica gel 60 plates in the solvent N,N-dimethylformamide/methanol/ethylene glycol/glacial acetic acid/1-chlorobutane/chloroform (4/35/6/0.4/18/20 by volume) separates porphyrin carboxylic acids by the number of free carboxyl groups. Coproporphyrins I and III and isocoproporphyrin are separated in 30 min, other porphyrins in 15 min. The N,N-dimethylformamide and acetic acid in the solvent strongly increase porphyrin fluorescence on the plates. Fading and diffusion of the fluorescent patterns is prevented by storage of the plates in the cold and dark without oxygen and with desiccant. In a preliminary step, porphyrins are purified in high yields, concentrated, and deacidified rapidly (2 min) by reversephase chromatography on cartridges containing a C₁₈ spacer or on Amberlite XAD-2 columns. The methods are applied to urines of porphyria patients and for following porphyrin ester hydrolysis.     

A new route to polyamino acids containing histidine

A new route for the synthesis of polyamino acids containing histidine is described and illustrated in the preparation of poly l-histidine. This method involves the use of the 2,4-dinitrophenyl group for the protection of the imidazole imino-nitrogen during polymerization. The N-carboxy anhydride of N^Im-DNP-l-histidine was polymerized to yield poly (DNP-l-histidine) with an average molecular weight of 29,400. After polymerization, the protecting groups were removed under very mild reaction conditions by thiolysis with mercaptans in N,N′-dimethylformamide (22 °). The mildness of the conditions for deblockage allows the preparation of histidine-containing polyamino acids and polypeptidyl proteins which could not be prepared by the previously available methods.     

N-Halamine-coated cotton for antimicrobial and detoxification applications

A new N-halamine precursor, 3-(2,3-dihydroxypropyl)-7,7,9,9-tetramethyl-1,3,8-triazaspiro[4.5]decane-2,4-dione (TTDD diol), was synthesized and bonded onto cotton fabrics. Fabrics with variable amounts of chlorine loading were prepared by using several concentrations of TTDD diol. A second N-halamine precursor, 3-(3-triethoxysilylpropyl)-7,7,9,9-tetramethyl-1,3,8-triazaspiro[4.5]decane-2,4-dione (TTDD siloxane), was also synthesized and bound to cotton for comparison purposes. The coated cotton fabrics contained two types of N–Cl moieties after chlorination of the amine and amide groups. Swatches with variable chlorine loadings were challenged with Staphylococcus aureus and Escherichia coli O157:H7 as a function of contact time. The biocidal test results showed that the chlorine loadings and surface hydrophobicities influenced the antimicrobial efficacies. The chlorinated swatches have also been employed to oxidize the simulant of chemical mustard to the less toxic sulfoxide derivative.     

The synthesis of 1,2:5,6-di-O-isopropylidene-d-mannitol: a comparative study

Three different methods of acetonation of d-mannitol using (a) acetone and zinc chloride, (b), 2,2-dimethoxypropane, 1,2-dimethoxyethane, and tin(II) chloride, and (c) 2-methoxypropene, N,N-dimethylformamide, and p-toluenesulfonic acid were studied in detail and compared, using gas-liquid chromatographic techniques. In each reaction, isomeric diacetals are formed, but method a gives the 1,2:5,6-diacetal in the highest yield (63%). Methods b and c give a more complex mixture of acetals than proposed in the literature, and both methods are less economical than a. A new 1,2:3,6:4,5-tri-O-isopropylidene-d-mannitol could be separated, and its graded hydrolysis was compared to that of the 1,2:3,4:5,6-triacetal.     

Characterization of Clostridium thermocellum JW20

Clostridium thermocellum JW20 (ATCC 31549), which was isolated from a Louisiana cotton bale, grew on cellulose, cellobiose, and xylooligomers and, after adaptation, on glucose, fructose, and xylose in the pH range of 7.5 to 6.1 with T_opt of 60°C, T_max of 69°C, and T_min of above 28°C. Doubling times during growth on cellulose and cellobiose were 6.5 and 2.5 h, respectively. The G+C content of the DNA was 40 mol% (chemical analysis). Growth on cellulose as substrate was totally inhibited in the presence of more than 125 mM sodium sulfate, 300 mM sodium chloride, 250 mM potassium chloride, 200 mM calcium chloride, 125 mM magnesium chloride, 40 mM lactate, or 250 mM acetate. The ratio of the fermentation products ethanol to acetate plus H₂ decreased when the culture was agitated. Agitation otherwise increased the rate of cellulose degradation in a growing culture but not under nongrowth conditions or with cell-free culture supernatant containing the extracellular cellulase. Shaking lowered the concentration of H₂ in the culture broth and thus minimized inhibition by the H₂ formed. Externally added H₂ caused an increased formation of ethanol during growth on cellulose or cellobiose. However, at an atmospheric pressure as high as 355 kPa (50 lb/in²), H₂ did not cause significant growth inhibition beyond an increasing lag phase (up to 24 h). Several criteria to specifically prove the purity of C. thermocellum cultures were suggested.     

2-Substituted fortimicins by ring opening of 2-deoxy-1,2-epimino-2-epi-fortimicin B and by nucleophilic displacements of 2-O-(methylsulfonyl)fortimicin derivatives

Opening of the aziridine ring of 2-deoxy-1,2-epimino-2-epi-fortimicin B (10) has been effected with both chloride and azide. The reactions are both stereo- and regiospecific and give 2-chloro-2-deoxyfortimicin B (2c) and 2-azido-2-deoxy-fortimicin B (2d). The nucleophilic displacements of the methanesulfonate groups of some 1-N-benzyloxycarbonyl-2-O-(methylsulfonyl)fortimicin derivatives with chloride, azide, and cyanide in N,N-dimethylformamide are dependent both on the nature of the nucleophile and the specific 1-N-benzyloxycarbonyl-2-methanesulfonate employed as the substrate. Striking differences in the stereochemistry of the azide displacements with different 2-methanesulfonates are believed to have a conformational basis. 2-Amino-2-deoxyfortimicin A (1c) and both of the 2-epimeric 2-chloro-2-deoxyfortimicins A (1b) and (5) were prepared for antibacterial assay and the in vitro results are reported.     

Some reactions of 1,6-di-O-p-tolylsulphonyl-D-mannitol and its derivatives

Nucleophilic displacement of 4,4′-di-O-mesyl-α,α-trehalose hexabenzoate occurred very readily to give, by a double inversion, the thermodynamically more stable 4,4′-di-iodide in 93% yield with overall retention of configuration. Reductive dehalogenation of the 4,4′-di-iodide with hydrazine hydrate—Raney nickel followed by debenzoylation afforded 4,4′-dideoxytrehalose in high, overall yield. Alternatively, treatment of trehalose with sulphuryl chloride afforded 4,6-dichloro-4,6-dideoxy-α-D-galactopyranosyl 4,6-dichloro-4,6-dideoxy-α-D-galactopyranoside, which underwent selective dehalogenation at the secondary positions on treatment with hydrazine hydrate—Raney nickel. Subsequent nucleophilic displacement of the primary chlorine substituents with sodium acetate in N,N-dimethylformamide gave, after deacetylation, 4,4′-dideoxy-α,α-trehalose. Repeated treatment of the 4,4′,6,6′-tetrachlorotrehalose derivative with hydrazine hydrate—Raney nickel gave 4,4′,6,6′-tetradeoxy-α,α-trehalose. An alternative route to the tetradeoxy derivative was via thiocyanate displacement of the 4,4′,6,6′-tetramethanesulphonate. The tetrathiocyanate, formed in poor yield, was desulphurized with Raney nickel to give the tetradeoxytrehalose. Treatment of 4,6-dichloro-4,6-dideoxy-α-D-galactopyranosyl 4,6-dichloro-4,6-dideoxy-α-D-galactopyranoside with methanolic sodium methoxide yielded, initially, 3,6-anhydro-4-chloro-4-deoxy-α-D-galactopyranosyl 4,6- dichloro-4,6-dideoxy-α-D-galactopyranoside which was transformed into the 3,6:3′,6′-dianhydro derivative. Reductive dechlorination of the dianhydride proceeded smoothly to give the 3,6:3′,6′-dianhydride of 4,4′-dideoxytrehalose.     

Chlorophyll determination in intact tissues using n,n-dimethylformamide

Photosynthetic pigments from etiolated cucumber (Cucumis sativus var. Beit Alpha improved, Hazera Co., Gedera) cotyledons were extracted by direct immersion of the intact cotyledons into the solvent N,N-dimethylformamide (DMF). The solvent is especially efficient when pigment concentration is low; time and tools are saved and the loss of pigment that usually occurs in more complicated extraction procedures is prevented. The specific absorption coefficient of chlorophyll a in DMF was also determined.     

Lignin Peroxidase Oxidation of Aromatic Compounds in Systems Containing Organic Solvents

Lignin peroxidase from Phanerochaete chrysosporium was used to study the oxidation of aromatic compounds, including polycyclic aromatic hydrocarbons and heterocyclic compounds, that are models of moieties of asphaltene molecules. The oxidations were done in systems containing water-miscible organic solvents, including methanol, isopropanol, N, N-dimethylformamide, acetonitrile, and tetrahydrofuran. Of the 20 aromatic compounds tested, 9 were oxidized by lignin peroxidase in the presence of hydrogen peroxide. These included anthracene, 1-, 2-, and 9-methylanthracenes, acenaphthene, fluoranthene, pyrene, carbazole, and dibenzothiophene. Of the compounds studied, lignin peroxidase was able to oxidize those with ionization potentials of <8 eV (measured by electron impact). The reaction products contain hydroxyl and keto groups. In one case, carbon-carbon bond cleavage, yielding anthraquinone from 9-methylanthracene, was detected. Kinetic constants and stability characteristics of lignin peroxidase were determined by using pyrene as the substrate in systems containing different amounts of organic solvent. Benzyl alkylation of lignin peroxidase improved its activity in a system containing water-miscible organic solvent but did not increase its resistance to inactivation at high solvent concentrations.     

Formulae for determination of chlorophyllous pigments extracted with n,n-dimethylformamide

The extraction of chlorophylls in higher plant tissue using N,N-dimethylformamide expedites the process and enables the determination of small samples with low pigment level.     

Analysis of urinary N-acetyl-S-(N-methylcarbamoyl)cysteine, the mercapturic acid derived from N,N-dimethylformamide

Human biotransformation of the industrial solvent N,N-dimethylformamide gives raise to N-acetyl-S-(N-methylcarbamoyl)cysteine (AMCC) which has the longest half-life (about 23 h) among urinary metabolites of N,N-dimethylformamide. It could be used for monitoring industrial exposure over several workdays, by measuring it in urine samples collected at the end of the working week. This is consistent with the suggestions of the American Conference of Governmental Industrial Hygienists, which established a limit of 40 mg/l for the year 2000. An easy, cheap and user-friendly method has been developed for determination of urinary AMCC. Unlike currently available methods, it requires neither a time-consuming preparation phase nor gas chromatographic analysis with a nitrogen-phosphorus or mass detector. The method uses high-performance liquid chromatography (HPLC), with an UV detector at 436 nm. A 10-μl volume of urine is added to a carbonate–hydrogen carbonate buffer and mixed with a dabsyl chloride solution in acetonitrile. The reaction between AMCC and the reagent is performed at 70°C for 10 min. The ‘dabsylated’ product is stable for at least 12 h. After brief centrifugation, the solution is ready for HPLC analysis using a C₁₈ column (250×4.6 mm, 5 μm). The method is sensitive (detection limit 1.8 mg/l) and specific. It identified urinary AMCC in urine of 40 subjects not exposed to N,N-dimethylformamide with a median concentration of 3.9 mg/l. In urine samples from 20 workers exposed to N,N-dimethylformamide (5–40.8 mg/m³), AMCC concentrations ranged from 16 to 170 mg/l. Industrial toxicology laboratories with limited instrumentation will be able to use it in the biological monitoring of workers exposed to N,N-dimethylformamide.     

Derivatives of β-D-fructofuranosyl α-D-galactopyranoside

De-etherification of 6,6′-di-O-tritylsucrose hexa-acetate (2) with boiling, aqueous acetic acid caused 4→6 acetyl migration and gave a syrupy hexa-acetate 14, characterised as the 4,6′-dimethanesulphonate 15. Reaction of 2,3,3′4′,6-penta-O-acetylsucrose (5) with trityl chloride in pyridine gave a mixture containing the 1′,6′-diether 6 the 6′-ether 9, confirming the lower reactivity of HO-1′ to tritylation. Subsequent mesylation, detritylation, acetylation afforded the corresponding 4-methanesulphonate 8 1′,4-dimethanesulphonate 11. Reaction of these sulphonates with benzoate, azide, bromide, and chloride anions afforded derivatives of β-D-fructofuranosyl α-D-galactopyranoside (29) by inversion of configuration at C-4. Treatment of the 4,6′-diol 14 the 1,′4,6′-triol 5, the 4-hydroxy 1′,6′-diether 6 with sulphuryl chloride effected replacement of the free hydroxyl groups and gave the corresponding, crystalline chlorodeoxy derivatives. The same 4-chloro-4-deoxy derivative was isolated when the 4-hydroxy-1′,6′-diether 6 was treated with mesyl chloride in N,N-dimethylformamide.     

Unsaturated sugars. I. Decarboxylative elimination of methyl 2,3-di-O-benzyl-alpha-D-glucopyranosiduronic acid to methyl 2,3-di-O-benzyl-4-deoxy-beta-L-threo-pent-4-enopyranoside

Decarboxylative elimination of methyl 2,3-di-O-benzyl-α-D-glucopyranosiduronic acid (1) with N,N-dimethylformamide dineopentyl acetal in N,N-dimethylformamide gave methyl 2,3-di-O-benzyl-4-deoxy-β-L-threo-pent-4-enopyranoside (3). Debenzylation of 3 was effected with sodium in liquid ammonia to give methyl 4-deoxy-β-L-threo-pent-4-enopyranoside (4). Hydrogenation of 3 catalyzed by palladium-on-barium sulfate afforded methyl 2,3-di-O-benzyl-4-deoxy-β-L-threo-pentopyranoside (5), whereas hydrogenation of 3 over palladium-on-carbon gave methyl 4-deoxy-β-L-threo-pentopyranoside (6). An improved preparation of methyl 4,6-O-benzylidene-α-D-glucopyranoside is also described.     

A nuclear magnetic resonance study of the kinetics of ligand exchange reactions in uranyl complexes. VII. Acetylacetonate exchange in bis(acetylacetonato)(N,N-dimethylformamide)dioxouranium(VI)

The exchange reaction of acac(acetylacetonate) in UO₂(acac)₂dmf (dmf=N,N-dimethylformamide) in o-dichlorobenzene has been studied by the NMR line-broadening method. The exchange rate depends on the concentration of the enol isomer of acetylacetone in its low region, and approaches the limiting value in its high region. It is proposed that the exchange reaction proceeds through the mechanism in which the dissociation of one end of the chelated acac is the rate-determining step. The kinetic parameters for this step are as follows: k (25 °C)=5.03 × 10⁻³ s⁻¹, ΔH3=91.6 ± 3.8 kJ mol⁻¹, and ΔS3 =17.2 ± 10.5 JK⁻¹ mol⁻¹. The exchange rate becomes slower by the addition of free DMF. This may be due to the competition of DMF with the enol isomer of acetylacetone in attacking a four-coordinated intermediate in the equatorial plane.