Ehrlich reaction

Analytical and Test Methods. In addition to the modem spectroscopic methods of detection and identification of pyrroles, there are several chemical tests. The classical Runge test with HCl yields pyrrole red, an amorphous polymer mixture. In addition, all pyrroles with a free a- or P-position or with groups, eg, ester, that can be converted to such pyrroles under acid conditions undergo the Ehrlich reaction with p-(dimethylamino)henzaldehyde to give purple products. 

Mutation. For industrial appHcations, mutations are induced by x-rays, uv irradiation or chemicals (iiitrosoguanidine, EMS, MMS, etc). Mutant selections based on amino acid or nucleotide base analogue resistance or treatment with Nystatin or 2-deoxyglucose to select auxotrophs or temperature-sensitive mutations are easily carried out. Examples of useful mutants are strains of Candida membranefaciens, which produce L-threonine Hansenu/a anomala, which produces tryptophan or strains of Candida lipolytica that produce citric acid. An auxotrophic mutant of S. cerevisiae that requires leucine for growth has been produced for use in wine fermentations (see also Wine). This yeast produces only minimal quantities of isoamyl alcohol, a fusel oil fraction derived from leucine by the Ehrlich reaction (10,11). A mutant strain of bakers yeast with cold-sensitive metaboHsm shows increased stabiUty and has been marketed in Japan for use in doughs stored in the refrigerator (12). 

Amongst products isolated from Heliotropium spathulatum (Boraginaceae) were 9 mg of a new alkaloid which gave a positive Ehrlich reaction with p-dimethylaminobenzaldehyde The molecular formula determined by mass spectrometry is CisH2sNOs. What is the structure of the alkaloid given the set of NMR results 54 Reference is useful in providing the solution to this problem. Conditions CDCI3, 9 mg per 0.3 ml, 25 °C, 400 MHz ( //), 100 MHz ( C). (a) HH COSY plot ... 

Screening tests for PBG are based on its reaction with DMAB (modified Ehrlichs reaction ). We recommend the trace PBG test kit available from Thermo Electron (UK), which isolates PBG from urine by ion-exchange resin before the reaction with DMAB. Older screening methods, such as those of Schwartz or Hoesch, give false-positive results due to the reaction of DMAB with urea, which is abundant in urine. 

Lysed erythrocytes are incubated with the substrate ALA. The formed PBG is determined by the modified Ehrlichs Reaction. 

The base-catalyzed reaction at the activated methylene positions of the pyrrolinones and indolinones with aromatic aldehydes is a general reaction producing the benzylidene derivatives. Products of the Ehrlich reaction with pyrrolinones are generally yellow-orange... 

For glycoproteins, the formation of anhydro rings from hexosamine residues is important in chromogen formation, especially in relation to the Ehrlich reaction and its modifications (3). / -Elimination is involved in the removal of oligosaccharide or polysaccharide chains from the protein core of glycoproteins when they are attached by O-glycosidic linkages to serine or threonine residues. A subsequent -elimination may also... 

Blix (8, 9, 10) after mild acid hydrolysis of bovine submaxillary glycoprotein isolated a crystalline material called sialic acid which gave the direct and indirect Ehrlich reactions. Table I shows that similar substances were isolated by other workers from glycolipids (11, 12), other... 

In the early work the crystalline sialic acids were known to be reducing sugars, had carbonyl groups, and gave indirect and direct Ehrlich reactions. The empirical formulas were relatively simple, and in retro-... 

A-l-lysyl ( )-l-deoxyfructose gives indirect Ehrlich reaction... 

The salts of methylene derivatives of 2H- and 3//-pyrroles and -indoles are produced in the Ehrlich reaction (Scheme 32, Section 3.05.1.2.8) and they are also intermediates in the Vilsmeier-Haack reaction (Scheme 24, Section 3.05.2.1.6). Although 6-fV,fV-dimethyl-amino-l-azafulvene, i.e. 2-(Ar,Ar-dimethylaminomethylene)-2//-pyrrole, dimerizes spontaneously (see Section 3.05.2.5), the 6-aryl-6-Ar)Ar-dimethylamino-l-azafulvenes (514 R = aryl) can be isolated (71JCS(B)1405) but, curiously, they are more susceptible to reactions with nucleophiles at the 6-position than are the corresponding salts (B-77MI30508). The benzo[6 ]-1 -azafulvenes, obtained from the reaction of 2-formylindoles with dialkylamines, also dimerize spontaneously, but the isomeric benzo[c]-2-azaf ulvenes, derived from 3-formylindoles, are thermally more stable, although they are extremely moisture sensitive... 

Qualitatively, the presence of the nonulosaminic acids is best indicated by the brilliant-red coloration formed on addition of an acidic solution of p-dimethylaminobenzaldehyde (the so-called direct Ehrlich reaction ), and by the bright-purple coloration which develops upon boiling with Bial s reagent for several minutes at 100°. In addition, the nonulosaminic acids give a blue-violet coloration with Dische s diphenylamine reagent for deoxypentoses and a positive reaction in the tryptophan-perchloric acid test. Since no single one of these color reactions is absolutely specific for a nonulosaminic acid, it is advisable to carry out at least two of these for a qualitative analysis. For quantitative determinations, all four reactions have been employed, using either A/ -acetylneuraminic acid (m. p., 183-185° [a] —32.0°) or methoxyneuraminic acid [m. p., 200° (dec.) [a]o —55.0°] as colorimetric standards. 

For their detection, the papers may be sprayed with reagents commonly used for the detection of keto and aminodeoxy sugars. Those of particular value include the direct Ehrlich reaction, the orcinol-trichloroacetic acid reagent, the chlorine-benzidine reagent for the detection of —NH—CO— groupings, and the Bial reaction as modified by Bohm und Baumeister. The limit of detection with the orcinol-trichloroacetic acid reagent is reported to be 5 ixg. of V-acetylneuraminic acid. For the detection of methoxyneuraminic acid, ninhydrin may also be used. 

As has been indicated above, neuraminic acid (75) bears a close resemblance to the intermediates (70), and it is to be expected that its derivatives should show reactions similar to those predicted for these compounds. For instance, the positive Ehrlich reaction given by the derivatives of neuraminic acid may be explained by assuming a series of reactions similar to those of Scheme B, as follows. 

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