Naming esters

A newer method for the preparation of nitronic esters, namely utilizing the (9-trimethyl-silyl ester, has been reported and these are prepared by the reaction of alkylnitro compounds and (V,(V-bis(trimethylsilyl)acetamide. These nitronic esters also undergo cycloaddition with alkenes to produce isoxazolidines (equation 54) (74MIP41601, 74DOK109, 78ACS(B)ll8). 

The reaction of 1-octadecanol with octadecanoic acid230) was carried out in the corresponding ester, namely 1-octadecyl octadecanoate (C36 ester). The authors observed the following influence of the experimental parameters ... 

Some ten years later, Darwish and Braverman50,51 undertook a more extensive study of this rearrangement, which has revealed some unique features. These investigators examined the behavior of six different esters, namely allyl, crotyl, a-methylallyl, racemic and optically active a, y-dimethylallyl, cinnamyl and a-phenylallyl 2,6-dimethylbenzene-sulfinates under various reaction conditions. 

An exception to the above are fatty acid methyl esters, which, due to the reaction mechanism involving molecular rearrangements with excess S03, have to be sulfonated at a slightly higher mole ratio of S03 to methyl esters (namely, 1.15-1.20/L). Outside the reaction tubes, in the reactor jacket, cooling water is circulated to control the liquid-film temperature and removing the reaction heat. 

Note that ester names contain first the alcohol, then the acid portion and end in -ate. Thus, the ester from the reaction of ethanol with acetic acid is called ethyl acetate. 

The accumulation of inflammatory cells (leukocytes and macrophages) in the arterial wall is another inducer of hypertension. For example, it has been shown that NO blockade in the aortas in L-Nitro arginine methyl ester(NAME)-treated rats resulted in the accumulation... 

The well-known addition of tert-butyl chloride to ethylene by means of A1C13 without skeletal rearrangement is simply another example of the initiation step of a /-cat polymerisation, involving the insertion of the alkene into an ester, namely the C-Cl bond, which is activated by the A1C13, via a six-centred transition state (I), as shown in equation (ii) ... 

Like in Chapt. 7, we begin the discussion with acetates, since acetic acid is the simplest nontoxic acyl group, formic acid being less innocuous. An informative study was carried out to compare the kinetics of hydrolysis of two types of corticosteroid esters, namely methyl steroid-21-oates (which are active per se) and acetyl steroid-21-ols (which are prodrugs), as exemplified by methyl prednisolonate (8.69) and prednisolone-21-acetate (8.70), respectively [89]. In the presence of rat liver microsomes, the rate of hydrolytic inactivation of methyl steroid-21-oates was much slower than the rate of hydrolytic activation of acetyl steroid-21-ols. Thus, while the Km values were ca. 0.1 -0.3 mM for all substrates, the acetic acid ester prodrugs and the methyl ester drugs had Vmax values of ca. 20 and 0.15 nmol min-1 mg-1, respectively. It can be postulated that the observed rates of hydrolysis were determined by the acyl moiety, in other words by the liberation of the carboxylic acid from the acyl-enzyme intermediate (see Chapt. 3). 

Carbonic acid esters (alkoxycarbonyl derivatives) are diesters of general formula R-O-CO-O-R. A single mechanism operates in the HO -catalyzed (and presumably also in the enzyme-catalyzed) hydrolysis of carbonic acid esters, namely a rate-determining addition of the base to the carbonyl C-atom to form an intermediate whose breakdown yields the drug (ROH), C02, and an alcohol (R OH) (Fig. 8.7,a) [153],... 

The esters name usually comes from the acid and ends in the suffix ate as does the word acetate itself. The acetate group is made from acetic acid by replacing the carboxyl hydrogen with an 7 group ... 

Let us first remind ourselves of the two mechanisms for hydrolysis of an ester, namely acid-catalysed hydrolysis and base-catalysed hydrolysis (see Section 7.9.2). 

Treatment of the dichloromethyl derivative 472 with sodium cyanide gave290 an almost quantitative yield of the epimeric nitriles (480, 481). The mixture could not he separated by chromatographic methods, but differences in reactivity of the stereoisomers towards methanolic hydrogen chloride allowed isolation of only one ester, namely, 482 the trails cyanide underwent ready conversion into the methyl ester, whereas the cis compound gave a rather complicated mixture of products, with amide 483 being identified as the major component. Reduction of the ester group in 482, followed hydrolysis of the dichloromethyl group, afforded DL-t/ireo-DL- Y/o-octose, characterized as the heptaacetate, and identified as threo-ido-octito by comparison with an authentic sample. 

An interesting property of nitric esters, namely their ability to catalyse certain reactions of addition polymerization has been reported recently. Initially this observation was made by Rogovin and Tsaplina [66] while polymerizing styrene and methyl methacrylate in the presence of nitroglycerine. The latter amounted to 5-20 parts by weight corresponding to about 10% of the polymerized substance. As a result of the increased polymerization speed, the molecular weight of the polymer is smaller than if polymerization is carried out slowly. 

Fatty acid esters would be predicted to have little irritation or toxic effects. Ex vivo permeability studies conducted in porcine buccal mucosa showed significant permeation enhancement of an enkephalin from liquid crystalline phases of glycerine monooleate [32]. These were reported to enhance peptide absorption by a cotransport mechanism. Diethylene glycol monoethyl ether was reported to enhance the permeation of essential oil components of Salvia desoleana through porcine buccal mucosa from a topical microemulsion gel formulation [33]. Some sucrose fatty acid esters, namely, sucrose laurate, sucrose oleate, sucrose palmitate, and sucrose stearate, were investigated on the permeation of lidocaine hydrochloride [34], with 1.5% w/v sucrose laurate showing a 22-fold increase in the enhancement ratio. 

Finally, a fourth class of alkaloids has been discovered, apparently specific to the leaves of P. Lyallii (57). It consists of two unseparable products, 37 and 38, in the ratio 2 to 1, which readily give lyaloside (23) on mild methanolysis, along with two esters, namely, methyl ferulate and methyl sinapate (39 and 40, respectively). Elucidation of their structure was essentially based on NMR considerations (57). Graphical correlations between 1H- and 13C-NMR spectra, associated with analysis of the residual constant coupling during a step by step [200 Hz per 200 Hz from 0 (TMS) to 2000 Hz] off-resonance procedure, permitted the precise assignment of all the carbon atoms of the products (58). 

For a-bromo ketones and related compounds, enhancement of the enantioselectivities has been achieved by the addition of simple Lewis acids (e.g., BF3, Cp2TiCl2, or magnesium salts, which presumably form Lewis acid-Lewis base complexes with the carbonyl functions of the substrates).2627 The stereochemical effect of some Lewis acid additives on the reduction of a racemic a-bromo ester, namely ethyl 2-bromo-2-phenylpropanoate, is summarized in Scheme 27.2. 

The leaves harvested in summer gave the highest oil recovery (1.84%) and eugenol content (83%), whereas in the rainy season, the concentration of esters, namely, eugenyl acetate and benzyl benzoate, were comparatively higher (Kaul et al., 1996). Cinnamon leaves affected by leaf spot disease yielded less oil (1.2%), but the eugenol content was unaffected (Kaul et al., 1998). Rao et al. (2006) reported that the essential oil content (1.9-2.2%) and the chemical composition of C. verum leaves were not affected by storage up to a period of 15 months. 

Pyrethroids consist of pyrethrum and its synthetic pyrethrum analogs called synthetic pyrethroids. Pyrethrum is a solvent extract of dried flowers of Chrysanthemum cinerariaefo-lium. The active ingredients of pyrethrum are called pyrethrins. Pyrethrins consist of four esters, namely, pyrethrins I and II and cinerins I and II, which comprise the combination of two different alcohols (pyrethrolone and cinerolone) and two different acids (chrysan-themic acid and pyrethric acid), as follows ... 

An example is the synthesis of ethyl a-ethoxalylpropionate (R = CH,) in 70% yield. Ethyl oxalate and ethyl succinate form ethyl a-ethoxalyl-succinate (83%). In a mixed ester condensation, the use of a more reactive ester, such as the phenyl or biphenyl ester, helps to prevent side reactions. Simple heterocyclic esters, namely, ethyl nicotinate and ethyl 8-quinolinecarboxylate, undergo the mixed ester condensation in good yields. The internal condensation of ethyl adipate to give 2-carbethoxycyclopentanone (Dieckmann reaction) is an example of cyclization (81%). ... 

Achenbach et al. (100) isolated four new abietane-type esters namely 3-0-benzoylhosloppone, 3-0-cimiamoylhosloppone, 3-0-benzoylhinokiol and 3-0-benzoylhosloquinone from the root bark of the plant. 

Finally, the enzymatic nature of CPIA-cholesterol ester formation will be briefly mentioned. None of the enzyme preparations of three known biosynthetic pathways for cholesterol esters, namely, acyl-CoA cholesterol Q-acyltransferase (ACAT), lecithin cholesterol 0-acyltransferase (LCAT), nor cholesterol esterase, was effective in producing CPIA-cholesterol ester from the Ba isomer or CPIA. In contrast, the 9,000 g supernatant or microsomal fractions from liver or kidney homogenate were found to be capable of producing CPIA-cholesterol ester without the addition of any cofactors. As substrate, only the Ba isomer was effective, and none of the 3 other fenvalerate isomers nor free CPIA was effective. The hepatic enzyme preparation also catalyzed hydrolysis of fenvalerate, and in this case all the 4 isomers were utilized as substrates. These facts imply that CPIA-cholesterol ester is formed from the Ba isomer through a transesterification reaction via intermediary acyl-enzyme complex. 

Ester Name Number of Carbons Boiling Point C % Purity CAS Number... 

Esters An alcohol and a carboxylic acid form an ester. The first part of an ester name designates the alcohol portion and the second the acid portion (named in the same way as the carboxylate ion). For example, the ester formed between ethanol and ethanoic acid is ethyl ethanoate (common name, ethyl acetate), a solvent for nail polish and model glue. 

There are some specific spray reagents for the detection of phthalate esters namely, spray solution I (add some zinc powder to a 20% ethanolic resorcinol solution), spray solution II (2 M sulfuric acid), and spray solution III (40% aqueous potassium hydroxide solution). Procedure Spray with I, heat for 10 min at 150°C, spray with II, heat 10 min at OO C, and spray with III. Phthalate esters will appear as orange spots on a yellow background (48). Spectroscopic data UV... 

Finally, the low antimalarial activity observed for two additional marine cycloperoxides strictly related to peroxyplakoric acid B3 methyl ester, namely chondrillin, (61) [Fig. (23)] [81], and muqubilone, (62) [Fig. (23)] [82], provides other interesting suggestions. The insertion of a double bond within the 1,2-dioxane ring is evidently detrimental for the activity, while the presence of the methoxy group at C-3 exerts a pivotal role in the determination of the antimalarial activity for this group of molecules. Most likely, simple 1,2-dioxane molecules, that, like plakortin, are consistently active, possess other features that are able to compensate the lack of the methoxy group. 

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