Amides nitrophenyl

In some cases acid amide formation was observed on attempted deprotonation at oxaziridine ring carbon. 2-r-Butyl-3-(4 -nitrophenyl)oxaziridine (67) was converted to the anion of acid amide (68) by sodium amide (69TL3887), while 2-(4 -nitrobenzoyl)-3-phenyl-oxaziridine (69) afforded the diacylimide (70) by addition of cyclohexylamine to its benzene solution at room temperature (67CB2593). 

As revealed by IR-spectroscopy, the attachment of the polymer proceeds via acylation of aminopropyls absorbances of both amides (1650 cm-1) and esters (1740 cm-1) contribute to the spectrum of polyacrylate-coated aminopropyl-Aerosil (specific surface area 175 m2/g) [55], During the reaction, the accumulation of p-nitrophenyl ester groups in the support is accompanied by the liberation of p-nitrophenol into the contacting solution. Thus, the evaluation of the conformational state of adsorbing macromolecules can be performed by the simultaneous study of both processes by UV-spectroscopy as shown in Fig. 7. Apparently, at... 

In the course of this study, the authors determined /Lvalues for dibenzyl, methyl phenyl, methyl p-nitrophenyl, di-p-tolyl, di-isopropyl and tetramethylene sulphoxides and for diethyl, dipropyl and dibutyl sulphites. The /Lscales are applied to the various reactions or the spectral measurements. The /Lscales have been divided into either family-dependent (FD) types, which means two or more compounds can share the same /Lscale, family-independent (FI) types. Consequently, a variety of /Lscales are now available for various families of the bases, including 29 aldehydes and ketones, 17 carboxylic amides and ureas, 14 carboxylic acids esters, 4 acyl halides, 5 nitriles, 10 ethers, 16 phosphine oxides, 12 sulphinyl compounds, 15 pyridines and pyrimidines, 16 sp3 hybridized amines and 10 alcohols. The enthalpies of formation of the hydrogen bond of 4-fluorophenol with both sulphoxides and phosphine oxides and related derivatives fit the empirical equation 18, where the standard deviation is y = 0.983. Several averaged scales are shown in Table 1588. 

Reaction of p-nitrophenyl 2-(p-tolylsulfinyl)acetate 161 with aryl aldimines in the presence of imidazole was found to give /j-lactams 162 and amides 163206. In the cyclization, only the two 3,4-trans derivatives were formed out of a possible four diastereomeric pairs and, interestingly, the ratio of two diastereomeric pairs went up to 6.7 1. This means not only that internal asymmetric induction207 affords the trans derivative, but that also a relatively high asymmetric induction took place during the reaction. 

R =R =ArO R =Me or 4-nitrophenyl) in the presence of tert-butylamine do not rearrange but instead afford the amides (236) and the hydrazides (237). Some liberation of phenol may occur from (227 R1=ArO R =Ar) and thiswould arise either by attack by MeO- at phosphorus, or by elimination from the... 

Figure 5.11 NPIA is one of the shortest heterobifunctional reagents. It reacts with amine-containing molecules through its p-nitrophenyl ester end to produce amide bonds. The iodoacetyl group then can be used to couple with thiol compounds to give stable thioether linkages.

Figure 5.29 pNPDP reacts with amine-containing compounds by its p-nitrophenyl ester group to form amide bonds. After photoactivation of the diazo derivative with UV light, a Wolff rearrangement occurs to a highly reactive ketene intermediate. This group can couple to nucleophiles such as amines. 

Figure 5.30 PNP-DTP can modify amine-containing molecules through its p-nitrophenyl ester group to form amide bonds. Exposure of its photosensitive diazo group with UV light generates a highly reactive carbene that can insert into active C—H or N—H bonds.

Figure 6.1 The Wedekind trifunctional crosslinker can react with amine groups via its p-nitrophenyl ester to form amide bond linkages. The phenyl azide group then can be photoactivated with UV light to generate covalent bond formation with a second molecule. The biotin side chain provides binding capability with avidin or streptavidin probes.

The total synthesis of ( )-geissoschizine (30) was reported by Yamada et al. (156) in 1974. The geometrically pure p-nitrophenyl ester 272 was condensed with tryptamine, and then the resulting amide 273 was transformed to lactam aldehyde 274 by hydroxylation with osmium tetroxide, metaperiodate oxidation, and Pictet-Spengler cyclization. 

Serine peptidases can hydrolyze both esters and amides, but there are marked differences in the kinetics of hydrolysis of the two types of substrates as monitored in vitro. Thus, the hydrolysis of 4-nitrophenyl acetate by a-chy-motrypsin occurs in two distinct phases [7] [22-24]. When large amounts of enzyme are used, there is an initial rapid burst in the production of 4-nitro-phenol, followed by its formation at a much slower steady-state rate (Fig. 3.7). It was shown that the initial burst of 4-nitrophenol corresponds to the formation of the acyl-enzyme complex (acylation step). The slower steady-state production of 4-nitrophenol corresponds to the hydrolysis of the acetyl-enzyme complex, regenerating the free enzyme. This second step, called deacylation, is much slower than the first, so that it determines the overall rate of ester hydrolysis. The rate of the deacylation step in ester hydrolysis is pH-dependent and can be slowed to such an extent that, at low pH, the acyl-enzyme complex can be isolated. 

F. R. Murphy, V. Krupta, G. S. Marks, Drug-Induced Porphyrin Biosynthesis. XIII. Role of Lipophilicity in Determining Porphyrin-Inducing Activity of Aliphatic Amides after Blockade of Their Hydrolysis by Bis-(p-nitrophenyl)phosphate , Biochem. Pharmacol. 1975, 24, 883-889. 

Unfortunately, the size of the crystallographic problem presented by elastase coupled with the relatively short lifedme of the acyl-enzyme indicated that higher resolution X-ray data would be difficult to obtain without use of much lower temperatures or multidetector techniques to increase the rate of data acquisition. However, it was observed that the acyl-enzyme stability was a consequence of the known kinetic parameters for elastase action on ester substrates. Hydrolysis of esters by the enzyme involves both the formation and breakdown of the covalent intermediate, and even in alcohol-water mixtures at subzero temperatures the rate-limidng step is deacylation. It is this step which is most seriously affected by temperature, allowing the acyl-enzyme to accumulate relatively rapidly at — 55°C but to break down very slowly. Amide substrates display different kinetic behavior the slow step is acylation itself. It was predicted that use of a />-nitrophenyl amid substrate would give the structure of the pre-acyl-enzyme Michaelis complex or even the putadve tetrahedral intermediate (Alber et ai, 1976), but this experiment has not yet been carried out. Instead, over the following 7 years, attention shifted to the smaller enzyme bovine pancreatic ribonuclease A. 

Cycloamyloses have been studied extensively as models of a-chymotrypsin and other serine proteases. Chymotypsin works via a double displacement pathway in which the hydroxyl group of serine-195 acts as a nucleophile. This is shown in Scheme I. In nature, the substrate is an amide. Synthetic esters are also used in model studies and routine assays. Nitrophenyl and... 

Most recently, Baltzer and co-workers have incorporated a lysine-bound nicotinamide into a more complex peptide scaffold [75]. This approach takes advantage of the augmented reactivity of a lysine residue contained in a helix-turn-helix scaffold (as described previously [76]). An adjacent histidine is able to selectively catalyze the formation of an amide bond between activated esters and the lysine c-amino group under aqueous conditions. Thus, reaction of the 42-residue peptide LA-42 withp-nitrophenyl hT-methylnicotinate in an aqueous solution at pH 5.9 yields the nicotinoyl-functionalized peptide (Fig. 27). 

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