Methyl ester acid hydrolysis

Although the biosynthetic cascade hypothesis predicts the co-occurrence of endiandric acids D (4) and A (1) in nature, the former compound was not isolated until after its total synthesis was completed in the laboratory (see Scheme 6). Our journey to endiandric acid D (4) commences with the desilylation of key intermediate 22 to give alcohol 31 in 95% yield. The endo side chain is then converted to a methyl ester by hydrolysis of the nitrile to the corresponding acid with basic hydrogen peroxide, followed by esterification with diazomethane to afford intermediate 32 in 92% overall yield. The exo side chain is then constructed by sequential bromination, cyanide displacement, ester hydrolysis (33), reduction, and olefination (4) in a straight-... 

The alkylated 3,6-dialkoxy-2,5-dihydropyrazines are hydrolyzed by treatment with 0.25 N hydrochloric acid (2 equivalents of H+) at room temperature to give the hydrochlorides of the corresponding alkylglycine methyl ester 3 and the chiral auxiliary amino acid methyl ester 2. Hydrolysis of the dihydropyrazines 1 under more drastic conditions (10-30 equivalents of 6 N hydrochloric acid) yields the corresponding diketopiperazines which are very stable to further hydrolysis. Basification of the hydrochlorides with aqueous ammonia liberates the free a-amino esters. In general, the chiral auxiliary amino ester is separated by distillation. 

Low-molecular-weight a- and /3-amino esters are easily hydrolyzed merely by boiling with water. Also, aqueous barium hydroxide is employed in the preparation of several amino acids, e.g., /3-aminopropionic acid (72%) and a-methyl-y-dimethylaminobutyric acid (90%). m-Nitrobenzoic acid (96%) is best prepared from the corresponding methyl ester by boiling for 10 minutes with 20% sodium hydroxide. Longer heating gives a colored product, and the use of a more dilute base is unsatisfactory. y-Nitrovaleric acid is obtained from its methyl ester by hydrolysis with concentrated hydrochloric acid. ... 

Although many examples of reactions of cobalt-bound organic ligands exist, most of these have been carried out for synthetic purposes rather than as studies of mechanism or of the effect of the covalently bound cobalt moiety. Although many such transformations are quite simple, they frequently lead to organocobalt complexes which are difficult, or impossible, to obtain by direct alkylation. For example, Schrauzer and Windgassen [51] prepared carboxymethyl- and carboxyethyl-(pyri-dine)cobaloxime by hydrolysis of the corresponding methyl esters in concentrated sulfuric acid. Similarly, Brown and coworkers [58] prepared p- and w-carbo-xyphenyl(aquo)cobaloximes from their methyl esters by hydrolysis in 0.5 N KOH in aqueous methanol. 

Relative amounts of monomers in purified PHA (%, wt/wt), determined by GC and GC-MS of the respective 3-hydroxy fatty acid methyl esters after hydrolysis of the poly(HAMCL)s-Trace amounts (<0.1%, wt/wt). 

Watanabe Y, Nagao T, Nishida Y, Takagi Y, Shimada Y. 2007. Enzymatic production of fatty acid methyl esters by hydrolysis of acid oil followed by esterification. J Am Oil Chem Soc 84 1015-1021. 

Figure 3-8 a) The dissociation of substituted benzoic acids (X = substituent), and b) the hydrolysis of benzoic acid methyl esters. 

The Claisen condensation of an aliphatic ester and a thiazolic ester gives after acidic hydrolysis a thiazolylketone (56). For example, the Claisen condensation of ethyl 4-methyl-5-thiazolecarboxylate with ethyl acetate followed by acid hydrolysis gives methyl 4-methyl-5-thiazolyl ketone in 16% yield. 

Poly(acrylic acid) and Poly(methacrylic acid). Poly(acryHc acid) (8) (PAA) may be prepared by polymerization of the monomer with conventional free-radical initiators using the monomer either undiluted (36) (with cross-linker for superadsorber appHcations) or in aqueous solution. Photochemical polymerization (sensitized by benzoin) of methyl acrylate in ethanol solution at —78° C provides a syndiotactic form (37) that can be hydrolyzed to syndiotactic PAA. From academic studies, alkaline hydrolysis of the methyl ester requires a lower time than acid hydrolysis of the polymeric ester, and can lead to oxidative degradation of the polymer (38). Po1y(meth acrylic acid) (PMAA) (9) is prepared only by the direct polymerization of the acid monomer it is not readily obtained by the hydrolysis of methyl methacrylate. 

Secondary alcohols (C q—for surfactant iatermediates are produced by hydrolysis of secondary alkyl borate or boroxiae esters formed when paraffin hydrocarbons are air-oxidized ia the presence of boric acid [10043-35-3] (19,20). Union Carbide Corporation operated a plant ia the United States from 1964 until 1977. A plant built by Nippon Shokubai (Japan Catalytic Chemical) ia 1972 ia Kawasaki, Japan was expanded to 30,000 t/yr capacity ia 1980 (20). The process has been operated iadustriaHy ia the USSR siace 1959 (21). Also, predominantiy primary alcohols are produced ia large volumes ia the USSR by reduction of fatty acids, or their methyl esters, from permanganate-catalyzed air oxidation of paraffin hydrocarbons (22). The paraffin oxidation is carried out ia the temperature range 150—180°C at a paraffin conversion generally below 20% to a mixture of trialkyl borate, (RO)2B, and trialkyl boroxiae, (ROBO). Unconverted paraffin is separated from the product mixture by flash distillation. After hydrolysis of residual borate esters, the boric acid is recovered for recycle and the alcohols are purified by washing and distillation (19,20). 

Treatment of (89) with lead tetraacetate generates the unstable open-ring aldehyde (90) which is quickly converted to a dimethylacetal (91). Following basic hydrolysis of the methyl ester and acetates, the acetal is cleaved with aqueous acid to produce TxB2. A number of other approaches, including one starting from the Corey aldehyde, have been described (58). 

Expect some product contamination if feed components can react with water, eg, ester will be partially hydrolyzed to acid and alcohol fate of reaction product species depends on above rules, eg, methanol from methyl ester hydrolysis probably not stripped out of bottoms stream. 

Catalytic hydrogenation of the 14—15 double bond from the face opposite to the C18 substituent yields (196). Compound (196) contains the natural steroid stereochemistry around the D-ring. A metal-ammonia reduction of (196) forms the most stable product (197) thermodynamically. When R is equal to methyl, this process comprises an efficient total synthesis of estradiol methyl ester. Birch reduction of the A-ring of (197) followed by acid hydrolysis of the resultant enol ether allows access into the 19-norsteroids (198) (204). 

Olestra is prepared by a solvenfless transesterification process in which sucrose is treated with methyl ester of fatty acids in the presence of sodium methoxide between 100—180°C for 14 hours (68). The manufacturing process involves removal of the unreacted fatty acid esters by enzymic hydrolysis... 

Two important widely used sulfonic acids are known as TwitcheU s reagents, or as in Russia, the Petrov catalysts. These reagents are based on benzene or naphthalene ( ) and (12), [3055-92-3] and [82415-39-2] respectively. The materials are typically made by the coupling of an unsaturated fatty acid with benzene or naphthalene in the presence of concentrated sulfuric acid (128). These sulfonic acids have been used extensively in the hydrolysis of fats and oils, such as beef tallow (129), coconut oil (130,131), fatty methyl esters (132), and various other fats and oils (133—135). TwitcheU reagents have also found use as acidic esterification catalysts (136) and dispersing agents (137). 

Oils are mixtures of mixed esters with different fatty acids distributed among the ester molecules. Generally, identification of specific esters is not attempted instead the oils are characterized by analysis of the fatty acid composition (8,9). The principal methods have been gas—Hquid and high performance Hquid chromatographic separation of the methyl esters of the fatty acids obtained by transesterification of the oils. Mass spectrometry and nmr are used to identify the individual esters. It has been reported that the free fatty acids obtained by hydrolysis can be separated with equal accuracy by high performance Hquid chromatography (10). A review of the identification and deterrnination of the various mixed triglycerides is available (11). 

Optically Active Acids and Esters. Enantioselective hydrolysis of esters of simple alcohols is a common method for the production of pure enantiomers of esters or the corresponding acids. Several representative examples are summarized ia Table 4. Lipases, esterases, and proteases accept a wide variety of esters and convert them to the corresponding acids, often ia a highly enantioselective manner. For example, the hydrolysis of (R)-methyl hydratropate [34083-55-1] (40) catalyzed by Hpase P from Amano results ia the corresponding acid ia 50% yield and 95% ee (56). Various substituents on the a-carbon (41—44) are readily tolerated by both Upases and proteases without reduction ia selectivity (57—60). The enantioselectivity of many Upases is not significantly affected by changes ia the alcohol component. As a result, activated esters may be used as a means of enhancing the reaction rate. 

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). 

Methylsuccinic acid has been prepared by the pyrolysis of tartaric acid from 1,2-dibromopropane or allyl halides by the action of potassium cyanide followed by hydrolysis by reduction of itaconic, citraconic, and mesaconic acids by hydrolysis of ketovalerolactonecarboxylic acid by decarboxylation of 1,1,2-propane tricarboxylic acid by oxidation of /3-methylcyclo-hexanone by fusion of gamboge with alkali by hydrog. nation and condensation of sodium lactate over nickel oxide from acetoacetic ester by successive alkylation with a methyl halide and a monohaloacetic ester by hydrolysis of oi-methyl-o -oxalosuccinic ester or a-methyl-a -acetosuccinic ester by action of hot, concentrated potassium hydroxide upon methyl-succinaldehyde dioxime from the ammonium salt of a-methyl-butyric acid by oxidation with. hydrogen peroxide from /9-methyllevulinic acid by oxidation with dilute nitric acid or hypobromite from /J-methyladipic acid and from the decomposition products of glyceric acid and pyruvic acid. The method described above is a modification of that of Higginbotham and Lapworth. ... 

Of the alkyl esters, methyl esters are the most useful because of their rapid hydrolysis. The acid is refluxed with one or two equivalents of methanol in excess alcohol-free chloroform (or dichloromethane) containing about O.lg of p-toluenesulfonic acid (as catalyst), using a Dean-Stark apparatus. (The water formed by the... 

Example 4.3. The p value for alkaline saponification of methyl esters of substituted benzoic acids is 2.38, and the rate constant for saponification of methyl benzoate under the conditions of interest is 2 x 10 s . Calculate the rate constant for the hydrolysis... 

Schdpf and Thoma found that lupininic acid yielded a methyl ester (b.p. 120-2°/10 mm.) which had [aj — 19-4° to 5-8° in different batches. The f-ester furnished a gummy picrate, [a]J, ° — 41-8°, and on hydrolysis by hydrochloric acid gave a crystalline lupininic acid hydrochloride, m.p. 275°, — 13T°, identical with that described by Willstatter and Fourneau, whilst the d-ester, or ester of f-rotation below — 19-4°, furnished a crystalline picrate, m.p. 185°, [a]j, -f- 61-8°, from which pure d-epi-ester,-b.p. 126°/11 mm., [aJi, 54-8°, was prepared, this in turn yielding amorphous d-lupininie acid hydrochloride. The f-ester is convertible into ... 

The data given in the table for corynanthine are due to Foumeau and Fiore. Raymond-Hamet later found that corynanthine on alkaline hydrolysis gave a dextrorotatory acid, which Scholz confirmed and identified its methyl ester as yohimbine and suggested that corynanthine is a stereoisomeride of yohimbine. Fourneau and Benoit have confirmed that corynanthine on acid hydrolysis gives 1-corynanthic acid (m.p. 284°, [a]i) — 85-9° pyridine), but on alkaline hydrolysis, even in the cold, some racemisation occurs and the resulting acid is of low lasvo-rotation. They also point out that both yohimbine and corynanthine yield yohimbone on dehydrogenation cf., p. 504) and are probably stereoiso-merides. 

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