Diacetyl, Table

Other specific discovery assays have been used such as differential inhibition of a vancomycin resistant S. aureus strain and its susceptible parent, and an assay based on antagonism of the antibacterial activity by N,A/-diacetyl-L-Lys-D-Ala-D-Ala [24570-39-6] a tripeptide analogue of the dalbaheptides receptor. AppHcation of this latter test to 1936 cultures (90) led to the isolation of 42 dalbaheptides, six of which, including kibdelin (Table 3), parvodicin (Table 3), and actinoidin A2 (68) were novel. A colorimetric assay based on competition between horseradish peroxidase bound teicoplanin and the... 

For the present, for reasons discussed above, the diacetyl procedure is the method of choice for the Laboratory of Neonatology with equipment available at present. The importance of the assay for urea in the blood of infants is emphasized by the readiness with which the urea level responds to change in diet in the infant (1). This is seen in Table V. 

Table 13. Coalescene measurements of l-methyl-2-pheny 1-4,4-diacetyl triafulvene (227 in different solvents (from Ref.61 ...

The yield of cage reaction products increases with increasing viscosity of the solvent. The decomposition of diacyl peroxides was the object of intensive study. The values of rate constants of diacyl peroxides (diacetyl and dibenzoyl) decomposition (kf and initiation (ki = 2ekd) are collected in Tables 3.4 and Table 3.5. The values of e are collected in the Handbook of Radical Initiators [4]. 

Table 8.17 shows the scope of the reaction of acetylcobalt tetracarbonyl with polyenes. The reactions are regiospecific with the acetyl group adding to the terminal unsaturated carbon atom of the ir-electron system to produce the E-a,p-unsaturated ketones [9]. In the reaction with fulvenes [10], only the 1-acetyl and 1,4-diacetyl derivatives are formed, with no evidence of the 2-isomer. This is an indication of the relative stabilities of the cyclic it-allyl complexes, compared with the exocyclic complex. It has been postulated that, in the reactions of conjugated systems, the initial o-allyl adduct proceeds to the products via the it-allyl complex (cf Scheme 8.1), whereas in the case of unconjugated tt-systems, the initial o-adduct is more stable and tends to undergo a further carbonylation reaction. 

These static cis effects find their parallels in kinetic and thermodynamic cis effects observed in the solvolysis reaction (10) (154). Both the rate of the reaction and its equilibrium constant increased in the order diacetyl derivative [37b] (- [7 7]) > monoacetylderivative (18) > acetyl-free derivative [37f] (->-[75] Table 21). 

Erythrochelin from Saccharopolyspora erythraea is a coprogen-type siderophore (Table 2) with Ac = i and Ac = o-Ser-o-A, A -diacetyl-A -hydroxy-Om 413). 

A complex of 1102 with L-P-(3,4-dihydroxyphenyl)alanine (dopa), [UO2-(dopa)] , has been reported,and a series of acylhydrazone adducts (L) [U02L2(N03)2] (L = acetyl, benzoyl, salicoyl, diacetyl, or diformylhydra-zone) and [U02L3(N03)2] (L = acetylhydrazone) have been described. The X-ray photoelectron spectral information obtained from uranyl complexes of 8-hydroxyquinoline is given in Table 3. The U 4/, 2 levels in the two... 

Brydon and Roberts- added hemolyzed blood to unhemolyzed plasma, analyzed the specimens for a variety of constituents and then compared the values with those in the unhemolyzed plasma (B28). The following procedures were considered unaffected by hemolysis (up to 1 g/100 ml hemoglobin) urea (diacetyl monoxime) carbon dioxide content (phe-nolphthalein complex) iron binding capacity cholesterol (ferric chloride) creatinine (alkaline picrate) uric acid (phosphotungstate reduction) alkaline phosphatase (4-nitrophenyl phosphate) 5 -nucleotidase (adenosine monophosphate-nickel) and tartrate-labile acid phosphatase (phenyl phosphate). In Table 2 are shown those assays where increases were observed. The hemolysis used in these studies was equivalent to that produced by the breakdown of about 15 X 10 erythrocytes. In the bromocresol green albumin method it has been reported that for every 100 mg of hemoglobin/100 ml serum, the apparent albumin concentration is increased by 100 mg/100 ml (D12). Hemolysis releases some amino acids, such as histidine, into the plasma (Alb). 

IV-acetyl pyrrolidines and -piperidines to the corresponding diones or ketones were similarly effected [405, 406], as were conversions of diacetyl and dibenzyl piperazines to diketo componnds by the same system (Table 5.1) [407]. Methylene groups adjacent to the N atom in tertiary polycyclic amines were oxidised by RuO /aq. NaCIO j/CCl (Fig. 5.5) [408]. A large-scale oxidation of l,4-bis(2-phenylethyl) piperazine to the dione was made by RnO /aq. Na(10 )/Et0Ac [409], and RuO /aq. Na(IO )/CCl converted dialkyl or diaryl A A -dimethyladenosines to the corresponding monoamido derivatives (Fig. 5.4) [410]. 

A number of examples involving nitrile oxide cycloadditions to cyclic cis-disubstituted olefinic dipolarophiles was presented in the first edition of this treatise, notably to cyclobutene, cyclopentene, and to 2,5-dihydrofuran derivatives (15). The more recent examples discussed here also show, that the selectivity of the cycloaddition to 1,2-cis-disubstituted cyclobutenes depends on the type of substituent group present (Table 6.8 Scheme 6.41). The differences found can be explained in terms of the nonplanarity (i. e., pyramidalization) of the double bond in the transition state (15) and steric effects. In the cycloaddition to cis-3,4-diacetyl-(197) and cis-3,4-dichlorocyclobutene (198), the syn-pyramidalization of the carbon atoms of the double bond and the more facile anti deformability of the olefinic hydrogens have been invoked to rationalize the anti selectivity observed. 

By comparison, a series of mostly monoacylated flavonols is known to date and recent reports increased the number slightly. Four new products came from Pseudognaphalium robustum and Tanacetum microphyllum (both Asteraceae), and from Adina cordifolia (Rubia-ceae). A diacetylated compound (3,5-diacetyltambulin) was recently isolated from the bark of Zanthoxylum integrifoliolum (Rutaceae). Since most of the flavonols are monoacylated, the accumulation of quercetin tetraacetate in Adina cordifolia is a remarkable result. Altogether, the newly reported compounds occur scattered in the plant kingdom their occurrence is so far of little chemosystematic value. Aerial parts of Tanacetum microphyllum (Asteraceae) yielded a derivative, which is structurally not an ester. It is, indeed, a carbo-methoxy derivative of 6-hydroxyluteolin-4 -methyl ether (compound 34 in Table 12.5). No other flavonoid of this type is known so far. 

Table II. Rates of Scrambling of Carbonyl Label in Diacetyl Peroxide at 80°C.

The adverse effects of various oximes (Including diacetyl-monoxime, which was not used at Edgewood) in humans are listed In Tables 2-2 through 2-7. These tables list only significant findings. 

Table 12 shows the chemical shift for the CH-CH part of selected (/ ,/ )-tartaric acid monoesters of amino alcohols, mainly well-known /1-blockers. As can be easily seen, the chemical shifts of the (R)- and (S)-amino alcohol derivatives lie within a narrow range, dependent on the kind of tartaric acid used. Monoesters of a-amino (/f)-alcohols with (R,R)-0,0-diacetyl- or... 

Aliphatic carbonyl compounds, such as diacetyl, which has a butter-like odour, also may contribute to the aromas derived from the MaiUard reaction, and many of the Strecker aldehydes also have characteristic aromas (Table 12.1). 

The production of fermented milks no longer depends on acid production by the indigenous microflora. Instead, the milk is inoculated with a carefully selected culture of LAB and for some products with LAB plus lactose-fermenting yeasts (Table 10.12). The principal function of LAB is to produce acid at an appropriate rate via the pathways summarized in Figure 10.12. The yoghurt fermentation is essentially homofermentative but the characteristic flavour of cultured buttermilk is due mainly to diacetyl which is produced from citrate by Lactococccus lactis ssp. lactis biovar diacetylactis, which is included in the culture for this product (Figure 10.31). 

The antisymmetric structure 494 has been proposed for the (V,7V-diacetyl-2,5-dimethyltetrazine.377,378 High energy barriers (Table XXXI) have been found for a variety of l,2,3,4-tetrahydro-l,2,4,5-tetrazines (495).379... 

Apart from ethyl acetate, the least reactive ester studied is N,0-diacetyl serinamide, which is hydrolyzed in a pH-independent reaction between pH 7 and 8 with a rate coefficient193 of 2.66 x 10-5 sec-1. Salmi and Suonpaa194 and Palomaa et al. 9S, have measured the rates of neutral hydrolysis of a number of chloroacetate esters, and this work has been extended more recently by Euranto and Cleve196-198, who have measured the activation parameters for the hydrolysis of several compounds. Motfat and Hunt199 have obtained the same data for the hydrolysis of a variety of alkyl and aryl trifluoroacetates, and the data for substituted phenyl acetates191 have been plotted in Fig. 14. Most of the available data are collected in Table 27. 

Early workers appeared to show that electrophilic substitution reactions could not be carried out on porphyrins, and began to question the aromaticity of porphyrins since this classical pre-requisite of aromatic character could not be accomplished. However, they had concentrated on reactions of metal-free systems, and since many electrophilic substitution reactions utilize acidic conditions (nitration, sulfonation), they were actually dealing with the non-nucleophilic porphyrin dication. But, as early as 1929, H. Fischer had realised that diacetylation of deuteroporphyrin-IX (Table 1) had to be carried out on a metal complex, such as the iron (III) derivative chelation with a metal ion which cannot be removed under the acid conditions of the subsequent reaction, effectively eliminates dication formation. A judicious choice of metal complex therefore needs to be made for any particular reaction. For example, though magnesium(II) produces an extremely reactive substrate for electrophilic substitution reactions, it is removed by contact with the mildest of acids and is, consequently, of little use for this purpose. 

Rothe (5, , 1 5) calculated the aroma values of some volatiles identified in the crumb of wheat bread and the crust of rye bread. The data listed in Table I indicate that ethanol, isobutanal, iso-pentanal, diacetyl and isopentanol contribute with high aroma values to the aroma of the wheat bread crumb. During baking of rye bread, the two Strecker aldehydes, isobutanal and isopentanal, increased so much in the crust that they showed the highest aroma values of the volatiles investigated. 

Table I. Strecker-Aldehydes Produced by Microwave and Conventional Heating of Amino Acids and Diacetyl...

Microwave Cake and Conventional Cakes. Losses of diacetyl and acetoin (Table VII) were.much greater in the microwave cake than in the cake prepared by conventional heating. Losses in the microwave were attributed to volatilization, although flavor binding by starches and proteins is also a factor. 

A general comparison of the first 32 minutes of the total ion chromatograms (TIC) for batter, microwave, and conventionally baked cakes are shown in Figure 1. Preliminary identifications and the retention times of seme significant volatiles shown in the TIC s of the three sample extracts are listed in Table 1. Upon examination, similarities were observed between the three sample chromatograms. In many instances, differences in appearance between the batter and cake samples were due to variation in the relative abundance of a compound alone or in relationship to other peaks. Examples of some compounds found to be in the batter control and the two cake samples include diacetyl, C4-C10 aldehydes, C4-C10 alcohols, C8-C11 dienals,... 

Calvert and Hanst88 using infrared analysis, have also re-investigated the photooxidation of acetaldehyde at 20°C. using 3130 A. radiation. Acetaldehyde pressures were chiefly about 42.5 nun., but the oxygen pressure was varied from 0 to 745 mm. Analyses were made for carbon monoxide, carbon dioxide, formic acid, methanol, acetic acid, peracetic acid, acetyl peroxide, methyl hydroperoxide, and unreacted acetaldehyde (Table X). Chains were short. Although they do not detect methyl hydroperoxide or diacetyl peroxide, the non-observance of a peroxide does not necessarily mean it is not formed. The decomposition of hydroperoxides on the smallest particle of catalyst is remarkably fast. 

Reference to Table 7.26 shows the dysprosium diacetyl monoxime complex to have seven molecules of water. This complex loses two molecules of lattice water at 160°C. At 230°C, the remaining five coordinated water molecules are lost from the complex. 

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