Acids from esters

Anilides or p-toluidides of acids from esters. Esters are converted into the corresponding anilides or p-toluidides by treatment with anilino- or with p-toluidino-magnesium bromide, which are readily obtained from any simple Grignard reagent and aniline or p-toluidine ... 

Other reactions useful for the protection of carboxylic acids are included in Section 107 (Esters from Carboxylic Acids and Acid Halides) and Section 23 (Carboxylic Acids from Esters). 

Very recently, Mordini and coworkers" have overcome the problems associated with the long reaction times that are normally required for the synthesis of hydroxamic acids from esters by performing these transformations under MW irradiation. The protective groups are also well tolerated under these reaction conditions, though a partial deprotection of the feri-butoxycarbonyl (Boc) group was observed in the reaction with Boc-proline ester. Amidic bonds and ketals also survive without any detectable decomposition. All the reactions go to completion in about six minutes, except in the case of the conversion of Boc-protected phenylalanine methyl ester, which required longer reaction times (12 min). 

PHENOLIC ACIDS BIOAVAILABILITY Release of Phenolic Acids from Esters... 

Quillaia bark or soapbark is derived from the tree Quillaja saponaria (Rosaceae) and other Quillaja species found in Chile, Peru, and Bolivia. The bark contains up to 10% saponins, a mixture known as commercial saponin , which is used for its detergent properties. Quillaia s surfactant properties are occasionally exploited in pharmaceutical preparations where it is used in the form of quillaia tincture as an emulsifying agent, particularly for fats, tars, and volatile oils. The bark contains a mixture of saponins which on hydrolysis liberates quillaic acid (Figure 5.62) as the aglycone, together with sugars, uronic acids, and acids from ester functions. 

Related Methods Carboxylic Acids from Esters (Section 23) Protection of Alcohols (Section 45A)... 

Problem 13.51 Inorganic acids such as H2S04, H3P04, and HOC1 (hypochlorous acid) from esters. Write structural formulas for (a) dimethyl sulfate, (b) tribenzyl phosphate, (c) diphenyl hydrogen phosphate, (d) f-butyl nitrite, (e) lauryl hydrogen sulfate (lauryl alcohol is n-C ]H23CH2OH), (/) sodium lauryl sulfate. ... 

Scheme 4 Mechanism for the release of carboxylic acids from esters 67.

Finally, ortAo-nitrobenzyl chromophores have been used to photorelease carboxylic acids from esters [111], but as in the case of amides [Eq. (12), Sec. 

Another early discovery was that CALB accepts H202 as nucleophile to produce peroxycarboxylic acids from esters or carboxylic acids (perhydrolysis activity can also be found in other serine hydrolases) [46, 47]. The in situ formed peracid can subsequently be used to epoxidize an alkene by (non-enzymatic) Prileshajev epoxidation. Hence, oleic acid incubated with CALB and H202 will produce 9,10-epoxyoctadecanoic acid [48]. Other alkenes can be epoxidized by H202 and a catalytic amount of carboxylic acid (and CALB) (Scheme 13.2) [49],... 

Note that 3-keto sulfoxides are readily available by the reaction of esters with dimsylsodium (1, 310-311). The reaction thus constitutes a method for preparation of one-carbon homologated a-hydroxy acids from esters. 

More efficient in terms of the number of steps (six) and overall yield (41%) was a later synthesis from Boukouvalas and co-workers (Scheme 7.2) (302). Bis-silyl-protected 3-hydroxymethyl 2,4-dihydrofuran-2-one (359) was selectively deprotected/condensed with benzyloxyacetaldehyde to give the alcohol, which was protected as a pivalate ester and subjected to selective desilylation then TEMPO-mediated oxidation. The resulting aldehyde 361 was then cyclized with a Lewis acid. Elimination of pivalic acid from ester 362 gave mainly the desired ylidenebutenolide regioisomer and the natural product (348). 

Carboxylic acids from esters COOR COOH... 

Derivatives of propanoic acid. The sessile bond that differentiates acid from acid chloride, acid from amide, and acid from ester, respectively, is shown crossed by a wavy line. 

Mallinger, A., Gall, T. L., and Mioskowski, C. (2008). One-pot synthesis of tetronic acids from esters. Synlett, 386-388. 

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