4- butyl ester

The butyl ester was hydrolyzed enantioselectively by the Bacillus lentus protease-III, albeit at a slower rate. Racemic butyl ester (1.07 g) was added to 10 mL of pH 7.5 phosphate buffer and 1 mL of Bacillus lentus protease-III solution. After 6.5 hours, the optical purity of the unreacted ester was only 72%. After stirring for an additional 14 hours the optical purity reached 99.9%. 

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Methyl p-toluenesulphonate. This, and other alkyl esters, may be prepared in a somewhat similar manner to the n-butyl ester with good results. Use 500 g. (632 ml.) of methyl alcohol contained in a 1 litre three-necked or bolt-head flask. Add 500 g. of powdered pure p-toluene-sulphonyl chloride with mechanical stirring. Add from a separatory funnel 420 g. of 25 per cent, sodium hydroxide solution drop by drop maintain the temperature of the mixture at 23-27°. When all the alkali has been introduced, test the mixture with litmus if it is not alkaline, add more alkali until the mixture is neutral. Allow to stand for several hours the lower layer is the eater and the upper one consists of alcohol. Separate the ester, wash it with water, then with 4 per cent, sodium carbonate solution and finally with water. Dry over a little anhydrous magnesium sulphate, and distil under reduced pressure. Collect the methyl p-toluenesulphonate at 161°/10 mm. this solidifies on cooling and melts at 28°. The yield is 440 g. 

In each step of the usual C-to-N peptide synthesis the N-protecting group of the newly coupled amino acid must be selectively removed under conditions that leave all side-chain pro-teaing groups of the peptide intact. The most common protecting groups of side-chains (p. 229) are all stable towards 50% trifluoroacetic acid in dichloromethane, and this reagent is most commonly used for N -deprotection. Only /ert-butyl esters and carbamates ( = Boc) are solvolyzed in this mixture. 

Nonvolatile analytes must be chemically converted to a volatile derivative before analysis. For example, amino acids are not sufficiently volatile to analyze directly by gas chromatography. Reacting an amino acid with 1-butanol and acetyl chloride produces an esterfied amino acid. Subsequent treatment with trifluoroacetic acid gives the amino acid s volatile N-trifluoroacetyl- -butyl ester derivative. 

Butyl acrylate (2-propenoic acid butyl ester)... 

Esters. Most acryhc acid is used in the form of its methyl, ethyl, and butyl esters. Specialty monomeric esters with a hydroxyl, amino, or other functional group are used to provide adhesion, latent cross-linking capabihty, or different solubihty characteristics. The principal routes to esters are direct esterification with alcohols in the presence of a strong acid catalyst such as sulfuric acid, a soluble sulfonic acid, or sulfonic acid resins addition to alkylene oxides to give hydroxyalkyl acryhc esters and addition to the double bond of olefins in the presence of strong acid catalyst (19,20) to give ethyl or secondary alkyl acrylates. 

It has been found that the flavor of fmit can be increased by a process called precursor atmosphere (PA) (77). When apples were stored in a controlled atmosphere containing butyl alcohol [71-36-3] the butyl alcohol levels increase by a factor of two, and the polar products, butyl ester, and some sesquiterpene products increase significantly. The process offers the possibiUty of compensating for loss of flavor in fmit handling and processing due to improper transportation conditions or excessive heat. 

Ethyl and butyl esters of poly(vinyl methyl ether)/maleic anhydride (PVM/MA) copolymer were introduced in the early 1960s for use in hair sprays. These polymers also have free carboxy acid groups that can be neutralized. Recommended neutralization is 10%, but products can be found in the range of 5—30%, and recommended neutralizers include ammonium hydroxide, aminomethyl propanol, and triisopropano1 amine. These were the most widely used polymers in hair sprays before their use decreased dramatically in the early 1990s. 

The synthesis and the quantitative gas chromatographic analysis of stable, yet volatile, A/-trifluoroacetyl- -butyl esters of amino acids has been estabhshed (124). An extensive review of subsequent advances ia gas chromatographic iastmmentation has been provided (125). 

So-called pure acryUc latexes are employed for maximum durabiUty as required, for example, in high performance exterior latex paints. On the other hand, interior flat wall latex paints do not need the high resistance to exterior exposure and hydrolysis. The most widely used latexes for this appHcation are vinyl acetate copolymer latexes such as vinyl acetate/butyl acrylate (2-propenoic acid butyl ester) [141-32-2] copolymers having just sufficient... 

Unsaturated Hydrocarbons. Olefins from ethylene through octene have been converted into esters via acid-catalyzed nucleophilic addition. With ethylene and propjiene, only a single ester is produced using acetic acid, ethyl acetate and isopropyl acetate, respectively. With the butylenes, two products are possible j -butyl esters result from 1- and 2-butylenes, whereas tert-huty esters are obtained from isobutjiene. The C5 olefins give rise to three j iC-amyl esters and one /-amyl ester. As the carbon chain is lengthened, the reactivity of the olefin with organic acids increases. 

Thiacyclotrideca-2,4,10,12-tetraene-6,8-diyne 1 -oxide, 5,10-dimethyl- HNMR, 7, 717 (75JA640) 4-Thia-2,6-diazabicyclo[3.2.0]heptane-2-carboxylic acid, 7-OXO-, t-butyl ester X-ray, 7, 349 (B-72M151201) 5H-2aA -Thia-2,3-diazacyclopent[cd]indene, 2,3-dimethyl-6,7-dihydro-X-ray, 6, 1054 (72ACS343)... 

Mc2NH, MeOH, 0°, 75% yield. t-Butyl esters could be cleaved with HCl without affectipg the Peoc group. 

Isobutylene, cat. coned. H2SO4, CH Cl, 25°, 6-10 h, 93% yield. These conditions also convert carboxylic acids to /-butyl esters. 

The carboxamidomethyl ester was prepared for use in peptide synthesis. It is formed from the cesium salt of an A-protected amino acid and a-chloroacetamide (60-85% yield). It is cleaved with 0.5 M NaOH or NaHCOa in DMF/H2O. It is stable to the conditions required to remove BOC, Cbz, Fmoc, and r-butyl esters. It cannot be selectively cleaved in the presence of a benzyl ester of aspartic acid. ... 

Mel, CH3CN morpholine or diethylamine, methanol, 76-95% yield. These conditions also cleave tlie 4 -pyridyl derivative. The Pet ester is stable to the acidic conditions required to remove the BOC and r-butyl ester groups, to the basic conditions required to remove the Fmoc and Fm groups, and to hydrogenolysis. It is not recommended for use in peptides that contain methionine or histidine since these are susceptible to alkylation with methyl iodide. 

Note that a cumyl ester can be selectively cleaved in the presence of a r-butyl ester and a/3-lactam. ... 

The r-butyl ester is a relatively hindered ester, and many of the methods reported below should be—and in many cases are—equally effective for the preparation of other hindered esters. The related 1- and 2-adamantyl esters have been used for the protection of aspartic acid. ... 

Butyl esters are stable to mild basic hydrolysis, hydrazine, and ammonia they are cleaved by moderately acidic hydrolysis. 

A /-butyl ester is stable to the conditions needed to convert an o ,/3-unsaturated ketone to a dioxolane (HOCH2CH2OH, TsOH, benzene, reflux). ... 

KOH, 18-crown-6, toluene, 100°, 5 h, 94% yield.These conditions were used to cleave the /-butyl ester from an aromatic ester they are probably too harsh to be used on more highly functionalized substrates. 

Me2Sn(SMe)2, BF3-Et20, PhCH3, 0°, 3-24 Ji AcOH, 75-100% yield." An ethyl ester can be hydrolyzed in the presence of an MEC ester with 1 N aqueous NaOH-DMSO (1 1), and MEC esters can be cleaved in the presence of ethyl, benzyl, cinnamyl, and t-butyl esters as well as the acetate, TBDMS and MEM ethers. 

Diphenylmethyl esters are similar in acid lability to r-butyl esters and can be cleaved by acidic hydrolysis from 5-containing peptides that poison hydrogenolysis catalysts. 

The dibenzosuberyl ester is prepared from dibenzosubeiyl chloride (which is also used to protect —OH, —NH, and —SH groups) and a carboxylic acid (Et N, reflux, 4 h, 45% yield). It can be cleaved by hydrogenolysis and, like t-butyl esters, by acidic hydrolysis (aq. HCl/THF, 20°, 30 min, 98% yield). ... 

Thiol esters, which are more reactive to nucleophiles than are the corresponding oxygen esters, have been prepared to activate carboxyl groups for both lactoniza-tion and peptide bond formation. For lactonization S-f-butyl and S-2-pyridyP esters are widely used. Some methods used to prepare thiol esters are shown below. The S-r-butyl ester is included in Reactivity Chart 6. 

The TCBOC group is stable to the alkaline hydrolysis of methyl esters and to the acidic hydrolysis of r-butyl esters. It is rapidly cleaved by the supemucleophile lithium cobalt(I)phthalocyanine, by zinc in acetic acid, and by cobalt phthalocy-anine (0.1 eq., NaBH4, EtOH, 77-90% yield). 

Trimethylsilyl Ester 47. /-Butyldimethylsilyl Ester 50. 5-/-Butyl Ester 59. 2-Alkyl-l,3-oxazolines... 

Tests conducted by the Eastman Kodak Company have shown that tert-butyl azidoformate [Formic acid, azido, -butyl ester], also known as iert-butoxy carbonyl azide and 1-BOC azide, is a thermally unstable, shock-sensitive compound (TNT equivalence 45%). 

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