Esters P-nitro

Drop 1 g. of sodium into 10 ml. of ethyl alcohol in a small flask provided with a small water condenser heat the mixture until all the sodium has dissolved. Cool, and add 1 g. of the ester and 0-5 ml. of water. Frequently the sodium salt of the acid will be deposited either at once or after boiling for a few minutes. If this occurs, filter oflF the solid at once, wash it with a little absolute ethyl alcohol (or absolute methylated spirit), and convert it into the p-bromophenacyl ester, p-nitro-benzyl ester or S-benzyl-tso-thiuronium salt (for experimental details, see Section 111,85). If no solid separates, continue the boiling for 30-60 minutes, boil oflF the alcohol, allow to cool, render the product just neutral to phenolphthalein with dilute sulphuric or hydrochloric acid, convert the sodium salt present in solution into a crystalline derivative (Section 111,85), and determine its melting point. 

PHENOL P-NITRO- 0-ESTER WITH 0-DIETHYL PHOSPHOROTHIOATHE PHENOL, P-NITRO-, 0-ESTER WITH O.O-DIETHYL PHOSPHOROTHIOATHE PHOSPHOROTHIOIC ACID 0,0-DIETHYL O-(4-NITROPHENYL)ESTER PHOSPHOROTHIOIC ACID 0,0-DIETHYL O-(P-NITROPHENYL)ESTER P-NITRO-O-ESTER DE FENOL, CON FOSFOTIOATO DE O O-DIETILO PHOSPHOROTHIOIC ACID, 0,0-DIETHYL 0-(4-NITR0PHENYL) ESTER PARATHION LIQUID (USA)... 

Acid B.P. M.P. AnlUde p-Tolul- dide 1 Amide p-Bromo- phenacyl Ester p-Nitro- benzyi Ester p-Phenyl phenacyl Ester S-Benzyl- JO-thi- uronium Salt Other Derivatives... 

CfljHAoFeNgOeS, Iron(III) protoporphyrin IX dimethyl ester p-nitro-benzenethiolate, 42B, 377... 

MP 191° to 192,5°C, Two recrystallizations from aqueous ethanol gave the cinchonidine salt of the L-acid, MP 192,5° to 194°C. To the salt (2.9 g) in warm ethanol (50 ml) was added water (50 ml) and a slight excess (ca 10 ml) of N aqueous sodium hydroxide. The mixture was diluted with water, cooled, filtered from the precipitated base and the filtrate acidified with hydrochloric acid. Refluxing with 2 N ethanolic hydrogen chloride yielded p-nitro-N-phthaloyl-L-phenylalanine ethyl ester, according to U.S. Patent 3,032,585. 

The only nucleophile is the free amine In (22) and the most reactive electrophile is the p-nitro-phenyl ester in (21). These combine to give the tripeptide (23). 

The base-catalyzed joint reaction of nitroalkenes with thiophenol in the presence of aldehydes gives y-phenylthio-P-nitro alcohols in one pot (Eq. 4.5).8 The joint reaction of nitroalkenes with thiols and a,p-unsaturated nitriles (or esters) has also been achieved. (Eq. 4.6).9 P-Nitro sulfides thus prepared show unique reactivity toward nucleophiles or tin radicals. The nitro... 

Esters and ketones bearing P-nitro groups can be prepared in many ways. For example, the Diels-Alder reaction of methyl P-nitroacrylate is one typical case. Various cyclic dienes are prepared by this route, and the reactions of Eq. 7.121167 andEq. 7.122168 are exemplified. 

The i-poly(3HB) depolymerase of R. rubrum is the only i-poly(3HB) depolymerase that has been purified [174]. The enzyme consists of one polypeptide of 30-32 kDa and has a pH and temperature optimum of pH 9 and 55 °C, respectively. A specific activity of 4 mmol released 3-hydroxybutyrate/min x mg protein was determined (at 45 °C). The purified enzyme was inactive with denatured poly(3HB) and had no lipase-, protease-, or esterase activity with p-nitro-phenyl fatty acid esters (2-8 carbon atoms). Native poly(3HO) granules were not hydrolyzed by i-poly(3HB) depolymerase, indicating a high substrate specificity similar to extracellular poly(3HB) depolymerases. Recently, the DNA sequence of the i-poly(3HB) depolymerase of R. eutropha was published (AB07612). Surprisingly, the DNA-deduced amino acid sequence (47.3 kDa) did not contain a lipase box fingerprint. A more detailed investigation of the structure and function of bacterial i-poly(HA) depolymerases will be necessary in future. 

Erdmann and Uhrich (2000 Erdmann et al., 2000) recently synthesized novel poly(anhydride-co-ester)s containing salicylic acid in the backbone, by melt polycondensation of the disalicylic acid ester of sebacic acid, poly[bis(o-carboxyphenoxy)sebacate] (PCPS) and the copolymer P(CPH-CPS). The release of salicylic acid (the active form of aspirin) from the former was studied in vitro and from the latter was studied in vivo (Erdmann and Uhrich, 2000 Erdmann et al., 2000). Similar polymers that release 5-amino salicylic acid, and p-nitro salicylic acid have been prepared... 

Support for the above view comes from NMR studies of the binding of phenyl and nitrophenyl acetates to a-CD (Komiyama and Hirai, 1980). These indicate that the nitro groups are located in the CD cavity and that the acetoxyl groups of the esters are held outside, more or less close to the secondary hydroxyls of the CD. It was calculated that the distance between the ester carbonyl carbon and the secondary hydroxyls decreases as p-nitro > phenyl > m-nitrophenyl, consistent with the observed order of rate acceleration (Komiyama and Bender, 1984). 

Other types of ester have been studied (Fendler and Fendler, 1975 Bender and Komiyama, 1978 Szejtli, 1982), though in much less detail. Brass and Bender (1973) studied the cleavage of two diaryl carbonates and three diaryl methylphosphonates in basic buffers (Table A5.ll). For the carbonates, reacting with /1-CD, introduction of p-nitro groups increases the acceleration ratio and worsens substrate binding, so that KTs barely alters. More interesting are the results for the phosphonates in that the effects of nitro groups depend on their position and on the CD. 

MW Williams, GT Young. Amino-acids and peptides. Part XXXV. The effect of solvents on the rates of racemisation and coupling of some acylamino-acid p-nitro-phenyl esters. The base strength of some amines in organic solvents, and related investigations. J Chem Soc Perkin Trans 1 1194, 1972. 

T. M. Kitson, The Action of Cytoplasmic Aldehyde Dehydrogenase on Methyl p-Nitro-phenyl Carbonate and p-Nitrophenyl Dimethylcarbamate , Biochem. J. 1989, 257, 579-584 T. M. Kitson, K. E. Kitson, A Comparison of Nitrophenyl Esters and Lactones as Substrates of Cytosolic Aldehyde Dehydrogenase , Biochem. J. 1996, 316, 225-232 T. M. Kitson, K. E. Kitson, Studies of the Esterase Activity of Cytosolic Aldehyde Dehydrogenase with Resorufin Acetate as Substrate , Biochem. J. 1997, 322, 701-708. 

The next question to be asked was whether or not this binding ability could be translated into correspondingly large acceleration of reaction rates. Royer and Klotz 89) investigated the rates of aminolysis of / -nitrophenyl esters using PEI with pendant apolar groups. The results of this study appear in Table IV. The rate constant for the reaction of lauroyl-PEI with p-nitro-... 

In 2008, the Rueping group reported the addition of nitroalkanes 78 to A-PMP-protected a-imino esters 79 in the presence of chiral phosphoric acid (R)-14r (10 mol%, R = SiPhj) (Scheme 29) [51]. This transformation provided P-nitro-a-amino esters 80 in good yields (57-93%), anrt-diastereoselectivities (2 1-13 1) and enan-tioselectivities (84-92% ee). 

A similar effect of the dipolarophile substituents is observed in the cycloadditions of the nitronate derived from trifluoronitroethane (84, Table 2.35) (24) In the absence of electron-withdrawing groups on the alkene, poor yields of the cycloadducts are obtained (entries 2 and 3). In addition, methyl substitution at either the a or p position of the dipolarophile significantly decreases both the rate and yield (entries 5 and 6). Similar results are observed with nitronates bearing with ester or nitro groups (16,25,26,34). 

This and other similar cycloadditions, however, when unactivated hydrocarbons without heteroatom substituents participate in Diels-Alder reaction, are rarely efficient, requiring forcing conditions (high temperature, high pressure, prolonged reaction time) and giving the addition product in low yield. Diels-Alder reactions work well if electron-poor dienophiles (a, p-un saturated carbonyl compounds, esters, nitriles, nitro compounds, etc.) react with electron-rich dienes. For example, compared to the reaction in Eq. (6.86), 1,3-butadiene reacts with acrolein at 100°C to give formy 1-3-cyclohexene in 100% yield. 

The p-nitro phenyl ester of N-carbobenzoxylysine reacts with water according to the following equation (B and P are just symbols used to simplify description of this compound H and O represent hydrogen and oxygen). 

Dihydroxy alcohols and amino alcohols in which the functional groups are not separated by more than four carbon atoms are effective acceptors. There is a general difference in the behavior of these compounds, however, in that hydroxyl alcohols decrease the rate of formation of p-nitro-phenol from p-nitrophenyl phosphate and amino alcohols increase the rate. Amino alcohols are relatively good nucleophiles in reaction with phosphate esters, perhaps because the amino group serves as a general base catalyst (143, 144)-... 

Molecular models show that during the course of the acylation reaction, the bound substrate is pulled partially out of the cyclodextrin cavity in forming the tetrahedral reaction intermediate. In other words, the model enzyme is not exhibiting the required transition state selectivity. Furthermore, excessively rigid substrates experience difficulty in rotating while bound in order to accommodate the need of the cyclodextrin hydroxyl group to attach perpendicular to the substrate ester plane, and subsequently rotate to become incorporated into the plane of the new ester product (Scheme 12.1). These problems were addressed by examination of substrates, such as p-nitro derivatives in which the ester protrudes further from the cavity, and substrates with more rotational flexibility such as alkyne 12.3. In these refined systems, much more enzyme-like rate accelerations of factors of up to 5 900 000-fold were observed for 12.4, for example. 

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