Glyoxal/DMSO

The choice between glyoxal/DMSO and formaldehyde is dictated by minor differences since the resolving power does not differ much (Miller, 1987) the glyoxal/DMSO method is somewhat more diffi-... 

C. Glyoxal/DMSO gel electrophoresis (McMaster and Carmichael, 1977 Thomas,... 

Although RNA can bind as well as DNA to nitrocellulose, reproducible results are obtained only if RNA is carefully denatured. Among formaldehyde, glyoxal/DMSO, methylmercuric hydroxide, alkali and heat, the first two are most effective and give best binding, whereas alkali pretreatment can even be counterproductive (Thomas, 1983 Henderson et al., 1991). Recently, some attractive alternatives to these standard methods have become available (see below). The transfer of RNA from gel to membrane is as for DNA, of which the downward alkaline capillary transfer is the most attractive (Table 9.1 lA). 

The one-electron reduction of 3,4,5-trimethoxyphenyl glyoxal with potassium tert-butoxide in DMSO gives rise mainly to the ctT-semidione, whereas on electrolysis in dimethylformamide, in the presence of tetraethylammonium perchlorate as the carrier electrolyte, the main product is the trans isomer (Sundaresan and Wallwork 1972 Scheme 3.47). 

Nitroform, Methanol, Hydrazine Nitroform, Diethyl ether, Hydrazine Nitroform, Methyl acetate, SUver-I oxide, 1,4-Dibromobutyne-2, Chloroform Glyoxal, Benzylamine, Formic acid, Acetonitrile, Acetic anhydride. Palladium on charcoal, Bromobenzene, Chloroform, Sulfolane, Nitrosonium tetrafluoroborate. Ethyl acetate TNT, DMSO, Oxygen gas. Sodium benzoate. Hydrochloric acid. Methanol, Acetone... 

Synthesis of Glycoluril la A modification of the literature procedure was used [33], To a solution of urea (600 g, 10 mol) in water (1 L) was added a 40% aq. solution of glyoxal (500 g, 3.45 mol) and cone. HC1 (86 mL). The resulting solution was heated at 85-90 °C until a heavy precipitate was formed. The reaction mixture was allowed to cool to room temperature and filtered. The filter cake was washed with copious amounts of water (2 L) followed by acetone to remove residual water. The resulting white solid (397.5 g, 81%) was dried under high vacuum. H NMR (DMSO, 400 MHz) 7.11 (s, 4H), 5.20 (s, 2H). 

A tandem Kornblum ox/daf/on/imidazole formation reaction was used during the preparation of new fluorescent nucleotides by B. Fischer and co-workers.The adenosine monophosphate free acid was mixed with 10 equivalents of 2-bromo-(p-nitro)-acetophenone and dissolved in DMSO. The required pH value was maintained with the addition of DBU which also served as a base. The Kornblum oxidation of the alkyl halide yielded the glyoxal, which reacted in situ with the aromatic amine to form the desired imidazole derivative. 

Although RNA is ss, it usually does not bind to membranes (Nygaard and Hall, 1963) due to the often considerable secondary structure. Alkali treatment is hardly possible (hydrolysis RNA) and DMSO dissolves nitrocellulose membranes. Glyoxal has been proposed by Thomas (1980) and has been widely used. Glyoxal binds to guanidine residues and the complex binds efficiently to nitrocellulose after which the glyoxal is removed by incubation at lOO C at pH 8.0. However, RNA should be free of protein which may react with glyoxal. 

Three different denaturants are currently employed formaldehyde glyoxal/dimethylsulfoxide (DMSO) or methylmercuric hydroxide (in order of decreasing popularity). It is also possible to elec-trophorese native RNA and denature RNA before transfer (3 gel volumes of 10% formaldehyde at 65°C for 30 min) (Khandjian and Meric, 1986). The sensitivity equals that obtained with denatured RNA. This approach can be useful for studying nicked RNA or to compare native with denatured RNA. Irrespective of the electrophoresis and transfer procedure to nylon, UV fixation was found to be beneficial. 

Synthesis of glyoxals. Mikol and Russell111 have prepared dimsylpotassium by the reaction of DMSO with potassium f-butoxide, and used the reagent in a general... 

Polymer 56, soluble in DMF or DMSO, can be prepared by the condensation of amino-substituted [Ru(bpy)3]2+ with glyoxal [112]. This polymer showed weaker emission than the free Ru chromophore that was attributed to less efficient intersystem crossing to the 3MLCT state. Similar condensation reactions with diacid anhydrides to produce polyimides have been reported [113]. These polymers showed long-wavelength emission associated with charge-transfer states. 

As the intermediate enamine reacts faster with imines than aldehydes, a one-pot three component coupling of the donor ketone, aldehyde and amine is possible. List and coworkers have achieved high ees in this reaction utilising L-proline (7.66) and some aliphatic aldehydes and aromatic aldehydes such as (7.136) in combination with p-anisidene (7.137). This catalyst system is also effective for the coupling of a-hydroxyketones. Use of the tetrazole-substituted proline (7.80) allows the reaction to be performed in dichloromethane rather than DMSO and high ees in the Mannich reaction between aliphatic ketones and imines derived from ethyl glyoxalate have been obtained imder these reaction conditions. 

In this reaction, initially, acetophenone 36 was converted to a-iodo acetophenone 39 by iodine, which was further transformed into phenyl glyoxal 40 by DMSO (dimethyl sulfoxide). The formed aldehyde then reacted with 2-aminothiophenol 37 to provide intermediate 41, which was further converted to 42 through an intramolecular 1,2-addition. Then, 42 underwent iodine-catalyzed oxidative dehydrogenation to afford the desired product 2-acyl benzothiazole 38 (Scheme 9.9). Very recently, the same authors reported the synthesis of 2,5-disubstituted oxazoles using a similar domino process [17]. 

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