5-methyl ester

This compound showed broad cytotoxic activity when evaluated against a panel of human cancer cell lines. 

---

Krilium The trade name of a soil conditioner. The solid form of Krilium has as active in-gredienl a copolymer of about equal molar proportions of vinyl ethanoate and the partial methyl ester of maleic acid. It may be formulated with lime, bentonite, etc. In aqueous form, Krilium contains a copolymer of about equal molar proportions of isobutene and ammonium maleamate. Other polymers are also used. 

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

Taft showed that LEER can also be established for aHphatic systems [8]. Taft compared the hydrolysis of substituted aliphatic methyl esters under basic conditions with the corresponding add-catalyzed reactions. 

This tetra ethyl ester is difficult to hydrolyse the corresponding tetra-methyl ester can, however, be hydrolysed to give ethane tetracarboxylic acid, (HOOC)jCH CH(COOH)j. The latter readily loses 2 molecules of carbon dioxide (on being heated or even on boiling with water) to give succinic acid, HOOCCHjCHjCOOH. 

The methyl ester formed by substituting methanol for ethanol in the above reaction has an even stronger odour and should be prepared if salicylic acid is suspected. 

In general the method is more satisfactory with esters of aromatic acids than with esters of aliphatic acids. Esters of alcohols other than methyl and ethyl are best treated by first converting them into methyl esters thus Heat together under reflux i ml. of the higher ester, 5 ml. of methanol and 0-2 g. of sodium methoxide. [In place of the sodium methoxide, it suffices to add o i g. of metallic sodium to the methanol.] After refluxing, distil off the excess of methanol (b.p, 65 ). The residue is then heated under reflux with benzylamine as described above. 

Formula M.p. Methyl ester M.p. Ethyl ester M.p. Acetyl deriv M.p. Benzoyl deriv M.p 3.5 Dinitro. benzoyl deriv. M.p. Naphthal- ene sulphonyl deriv. M.p. 

If the ester does not yield a benzylamide by this procedure, convert it into the methyl ester by refiuxing 1 g. for 30 minutes with 5 ml. of absolute methanol in which about 01 g. of sodium has been dissolved. Remove the methanol by distillation and treat the residual ester as above. 

The hydrazides are often crystalline and then serve as useful derivatives. Esters of higher alcohols should be converted first to the methyl esters by boiling with sodium methoxide in methanol (see under AT-benzylamides). 

Chiral 2-oxazolidones are useful recyclable auxiliaries for carboxylic acids in highly enantioselective aldol type reactions via the boron enolates derived from N-propionyl-2-oxazolidones (D.A. Evans, 1981). Two reagents exhibiting opposite enantioselectivity ate prepared from (S)-valinol and from (lS,2R)-norephedrine by cyclization with COClj or diethyl carbonate and subsequent lithiation and acylation with propionyl chloride at — 78°C. En-olization with dibutylboryl triflate forms the (Z)-enolates (>99% Z) which react with aldehydes at low temperature. The pure (2S,3R) and (2R,3S) acids or methyl esters are isolated in a 70% yield after mild solvolysis. 

The blocking and deblocking of carboxyl groups occurs by reactions similar to those described for hydroxyl and amino groups. The most important protected derivatives are /-butyl, benzyl, and methyl esters. These may be cleaved in this order by trifluoroacetic acid, hydrogenolysis, and strong acid or base (J.F.W. McOmie, 1973). 2,2,2-Trihaloethyl esters are cleaved electro-lytically (M.F. Semmelhack, 1972) or by zinc in acetic acid like the Tbeoc- and Tceoc-protected hydroxyl and amino groups. 

In his cephalosporin synthesis methyl levulinate was condensed with cysteine in acidic medium to give a bicyclic thiazolidine. One may rationalize the regioselective formation of this bicycle with the assumption that in the acidic reaction mixture the tMoI group is the only nucleophile present, which can add to the ketone. Intramolecular amide formation from the methyl ester and acid-catalyzed dehydration would then lead to the thiazolidine and y-lactam rings. The stereochemistry at the carboxylic acid a-... 

The oxidation of the cyclic enol ether 93 in MeOH affords the methyl ester 95 by hydrolysis of the ketene acetal 94 formed initially by regioselective attack of the methoxy group at the anomeric carbon, rather than the a-alkoxy ketone[35]. Similarly, the double bond of the furan part in khellin (96) is converted ino the ester 98 via the ketene acetal 97[l23],... 

One of the hydroxybenzoic acids is known by the common name salicylic acid Its methyl ester methyl salicylate occurs in oil of wintergreen Methyl salicylate boils over 50°C lower than either of the other two methyl hydroxybenzoates What is the structure of methyl salicylate Why is its boiling point so much lower than that of either of its regioisomers ... 

Aspartame is the market leader among artifi cial sweeteners It is a methyl ester of a dipeptide un related to any carbohydrate It was discovered in the course of research directed toward developing drugs to relieve indigestion... 

Methyl salicylate is the methyl ester of o hydroxybenzoic acid Intramolecular (rather than mtermolecular) hydrogen bonding is responsible for its relatively low boiling point... 

---