Esters replacement

Diana GD, Yolkots D, Nitz TJ, et al. Oxadiazoles as ester replacements in compounds related to disoxaril antirhinovirus activity. J Med Chem 1994 37 2421-2436. 

Acetylene dicarboxylic esters and (less easily) acetylene monocarboxylic esters replace nitriles from the 4,5-positions of 1,2,4,3-triazaphosphole rings (92) to give carboxyl derivatives of 1,2,3-diazaphospholes, presumably by a cycloaddition/cycloreversion mechanism, R/R = Me/Ph, SiMej/NMCj <83ZN(B)1484>. 

Table X shows a comparison between the ultraviolet spectral maxima obtained in this study and the literature values. The standard and collected GLC spectra are qualitatively the same. The characteristic shift to lower wavelength by an organophosphate oxon is evident. The shift to a lower wavelength when a phosphate ester replaces the H atom of the hydrolysis product is noted also (Diazinon).

When the enzyme is used to catalyse the synthesis of a peptide bond, the solvent is either non-aqueous or contains only a low concentration of water. In addition, of course, an amino component such as an amino acid or peptide ester replaces the water in the second step. Obviously, the amino component must be unprotonated for reaction to succeed. Synthesis is favoured over hydrolysis of the resultant peptide because an amide is kinetically a much worse substrate for a proteinase than is an ester. The rapid acylation of a proteinase by an TV-protected amino acid or peptide aryl ester can be demonstrated experimentally using a stopped-flow apparatus with spectrophotometric facilities. A rapid burst of phenol is followed by steady-state release, showing that acylation of the enzyme is faster than hydrolysis of the acy-lated enzyme. No such burst is detectable if, for example, an TV-acylated amino acid anilide is used as substrate. In fact, acylation is the rate-determining step with amide substrates. 

FIGURE 15.30 Ethyl oxime ether as ester replacement gave an improved bioavailability. 

Using an oxalic ester replaces a reactive hydrogen atom by an oxo ester (alkoxalyl) group.750 Thus diethyl 3-methyl-2-oxoglutarate is obtained in 70% yield from ethyl propionate and diethyl oxalate 751 and dimethyl dioxo-homonorcamphorate [methyl(3-methoxycarbonyl-2-oxocyclopentyl)glyoxalate] can be prepared in 90% yield from ethyl 2-oxocyclopentanecarboxylate and methyl oxalate 752... 

With the methyl ester replaced by a benzyl ester. Gray also prepared several compounds where the benzoyl portion of the cocaine molecule is replaced by other aroyl groups. The pharmacology is summarized in Table 4. 

A review on HIV-1 specific reverse transcriptase inhibitors has appeared, with special emphasis on TSAO-T (109) and related compounds. Some new analogues of TSAO-T and its TV -methyl derivative have been reported, with ethers and esters replacing the Tbdms group at 0-5, and also with aminogroups at C-5, and some of the ethers and amines had moderate activity. ... 

Thioethers from thiolsulfonic acid esters Replacement of C-formyl by alkylthio groups... 

Fatty acid esters of mono- and polyfunctional alcohols are the workhorses of oleochemistry. In many fields of application fatty acid methyl esters replace fatty adds because they are less corrosive. Chemical reactions can often be carried out under milder conditions. They have lower boiling points and require less energy to distil and to fractionate than the corresponding fatty acids. The elimination of methanol from the reaction products can be more easily achieved than that of water. Therefore fatty acid methyl esters are primarily used for the production of saturated and unsaturated fatty alcohols. Methyl esters are manufactured by acid catalyzed esterification of fatty acids in counter-current reaction columns or by alkaline transesterification starting directly from the triglyceride oils in a batch, semi-batch or continuous process (Figure 9.1.37> ° ° ... 

In the 1960s and 1970s, from ingredients of chrysanthemums, an important group of insecticides, the pyrethroids, was developed these are derived from chrysanthemic acid. The pyrethroids and the phosphate esters replaced the previously intensively applied chlorinated hydrocarbons such as, for example, DDT. 

The group on the ester can be varied from ethyl to methyl, butyl, trifluoro-ethyl. or 2-ethylhexyl. The reaction went well with electron-donating groups on the imidazo[1.2-a] pyridine. While the methyl at C-2 could be swapped out with an ester, replacing it with a trifluoromethyl caused the reaction to fail (14RSC Advances32013). 

Acetaldehyde, synthesis using metal catalysts, 118-119 Acetoacetate esters, replacement for isocyanates, 13... 

The structures of leucomycin Ai -Ag have been shown to be C2-C5 fatty acid esters replacing the isovaleryl group on mycarose in Ag the availability of these and of semisynthetic analogs made it possible to relate their structure and lipophilicity with biological activities. The structure of picromycin has been thoroughly revised to the lU-membered diketonic lactone (XIIl) which differs from narbomycin only by the presence of the tertiary alcohol group at C12. 

Although phosphate esters replace a portion of the flammable plasticizer in flexible PVC composites, these systems can be further enhanced with other options. Quite often, more than one mechanistic approach or blend of additives is the most cost-effective route. 

Methyl ester replaces free carboxyl group. DMSO = dime thy Isulfoxide. 

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