Esters general structure

The relative amounts of LDL and HDL cholesterol in your bloodstream depend, at least in part, on your diet In particular, they depend on the total amount and the type of fat that you eat. Fats (triglycerides) are esters of glycerol with long-chain carboxylic acids. The general structure of a fat can be represented as... 

The COOH group at one end of the ester molecule can react with another alcohol molecule. The OH group at the other end can react with an acid molecule. This process can continue, leading eventually to a long-chain polymer containing 500 or more ester groups. The general structure of the polyester can be represented as... 

A variety of ionomers have been described in the research literature, including copolymers of a) styrene with acrylic acid, b) ethyl acrylate with methacrylic acid, and (c) ethylene with methacrylic acid. A relatively recent development has been that of fluorinated sulfonate ionomers known as Nafions, a trade name of the Du Pont company. These ionomers have the general structure illustrated (10.1) and are used commercially as membranes. These ionomers are made by copolymerisation of the hydrocarbon or fluorocarbon monomers with minor amounts of the appropriate acid or ester. Copolymerisation is followed by either neutralisation or hydrolysis with a base, a process that may be carried out either in solution or in the melt. 

Figure 2S-1. Generalized structure of a plasma lipoprotein. The similarities with the structure of the plasma membrane are to be noted. Small amounts of cholesteryl ester and triacylglycerol are to be found in the surface layer and a little free cholesterol in the core.

Fig. 5.4 (Above and opposite) General structure of cephalosporins and examples of side-chains R and R. (R is —OCH3 in cefoxitin and cefotetan and —H in other members.) Cephalosporins containing an ester group at position 3 are liable to attack by esterases in vivo.

The TunaPhos ligands of general structure 114, when complexed with [RuPhCl2]2, bring about the asymmetric hydrogenation of /1-keto esters with... 

Thus, esters 304 have been obtained in medium to good yield <2002FA145, 2005ZOR109>, derivatives 305 bearing an isoquinolinium moiety have been prepared <2003JHC1041>, several derivatives of the general structure... 

Fig. 2.9.38. General structural formula of polyethoxylated sorbitan esters. 

Figure 12.2 Structure of waxes. The general structure of a wax is shown in which n and m are usually between 8 and 18. The structure of hexadecyl hexadecanoate (cetyl palmitate), a wax found in sperm whale oil, is shown. This is an ester of hexadecanoic (palmitic) acid and hexadecanol (cetyl alcohol).

Acyl glucuronides (i.e., ester glucuronides of general structure 11.6) are formed as conjugates of carboxylic acids. These compounds are rather uniquely reactive a) they are far more sensitive to chemical hydrolysis than ether... 

General structure of a fatty acid ester (R) of testosterone Girard hydrazone... 

A second example of the use of ionic chiral auxiliaries for asymmetric synthesis is found in the work of Chong et al. on the cis.trans photoisomerization of certain cyclopropane derivatives [33]. Based on the report by Zimmerman and Flechtner [34] that achiral tmns,trans-2,3-diphenyl-l-benzoylcyclopropane (35a, Scheme 7) undergoes very efficient (0=0.94) photoisomerization in solution to afford the racemic cis,trans isomer 36a, the correspondingp-carboxylic acid 35b was synthesized and treated with a variety of optically pure amines to give salts of general structure 35c (CA=chiral auxiliary). Irradiation of crystals of these salts followed by diazomethane workup yielded methyl ester 36d, which was analyzed by chiral HPLC for enantiomeric excess. The results are summarized in Table 3. 

In nonpolar media, on the other hand, the newly formed oxonium ion will either quickly convert to the corresponding soluble ester, or it will precipitate, since monomeric or short-chain oligomeric oxonium salts have low solubility in such media. The soluble ester is structurally similar to the initiator and may add another THF molecule. The resulting oxonium ion will again revert to the ester or precipitate. In fact, precipitates are generally observed durina the eairly stages of polymerization in media of low polarity. They have been isolated and characterized as monomeric or short chain oligomeric oxonium salts (17). 

The basis for the selective toxicity of malathlon provided the rationale for the design of the N-dlmethoxyphosphlnothloyl derivatives of methylcarbamates esters as selectively toxic Insecticides (general structure below). 

Many mechanisms had been proposed in the past to rationalize this selectivity (tri-oxanes, perepoxide, exciplex, dipolar or biradical intermediates) however, it is now generally accepted that the reaction proceeds through an intermediate exciplex which has the structural requirements of a perepoxide. This assumption is supported by (a) the lack of stereoselectivity in the reactions with chiral oxazolines and tiglic acid esters (b) the comparison of the diastereoselectivity of dialkyl substituted acrylic esters with structurally similar non-functionalized aUtenes (c) the intermolecular isotope effects in the photooxygenation of methyl tiglate and (d) the solvent effects on regioselectivity. ... 

Carbamate anticholinesterase agents are carbamic acid esters that are hydrolyzed by AChE in a manner similar to that of ACh. Carbamates have this general structure ... 

When deprotonated dimethyl sulfone is reacted with 2 equiv of benzonitrile, compound 109 is obtained in low yield (Equation 91) <1973JOM(59)53>. Compounds of the general structure 179 can be prepared from two molecules of enamino esters 288 and sulfur dichloride or disulfur dichloride <1984JOG4780> or in low yield using chlorocarbo-nylsulfenyl chloride 289 as the source of sulfur <1985JHC1621> (Equation 92). A series of cycloadditions lead to the formation of 131 from 290 and two molecules of the ynamine 291 (Scheme 69) <1995LA1795>. 

An enantioselective synthesis of the methyl esters of -)-cis and (-)-tro/ i-clavicipitic esters has been achieved <99T10989>. The key cyclisation step is the acid cyclisation of the amino acid ester 20. A number of tetracyclic derivatives of the general structure 21 have also been reported <99TL5569>. 

Figure 2.10 General structural formula of vinyl esters...

The free ortho acids have not been isolated because of their thermodynamic instability, and recent attempts aimed at their detection have not been reported [1], However, the ortho esters are stable derivatives which have the general structure I. Related to the ortho esters are derivatives in which the R, R",... 

Nitroxyethyl Nitramine Plasticizers Nitroxy ethyl nitramine (NENA) plasticizers are a new family of energetic plasticizers which have emerged recently. These are effective plasticizers in energetic formulations, particularly in nitrocellulosic systems. NENAs contain both nitrate ester and nitramine functionalities and possess the general structure RN (N02).CH2.CH2.0N02 where R is methyl, ethyl, propyl, isopropyl, butyl and pentyl. 

The general structure of erythromycin is shown with the macrolide ring and the sugars desosamine and cladinose. It is poorly soluble in water (0.1%) but dissolves readily in organic solvents. Solutions are fairly stable at 4°C but lose activity rapidly at 20°C and at acid pH. Erythromycins are usually dispensed as various esters and salts. 

In sulfamation, also termed IV-sulfonation, compounds of the general structure I NSC H are formed as well as their corresponding salts, acid halides, and esters. The reagents are sulfamic acid (amido—sulfuric acid), SO3—pyridine complex, S03—tertiary amine complexes, aliphatic amine—S03 adducts, and chlorine isocyanate—S03 complexes (3). 

Organophosphates are esters of phosphoric acid. They have the general structure illustrated below. 

Figure 13.17 General structure of phosphoric and thiophosphoric acid (thio)esters. Note that often Ri = R2 = CH3 or C2H5.

FIGURE 27-15 General structure of aminoacyl-tRNAs. The amino-acyl group is esterified to the 3 position of the terminal A residue. The ester linkage that both activates the amino acid and joins it to the tRNA is shaded pink. 

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