Mandelic acid ethyl ester

Maltol — see Pyran-4-one, 3-hydroxy-2-methyl-Maltol, ethyl — see Pyran-4-one, 3-ethoxy-2-methyl-Maltol, methyl — see Pyran-4-one, 3-methoxy-2-methyl-Mandelic acid ethyl ester, 1, 310-311 Manganaindene reactions, 1, 671 Mannich bases dehydro... 

It is preferably prepared by reacting mandelic acid ethyl ester with guanidine in boiling alcoholic solution whereby it is obtained as difficultly soluble precipitate with a yield of 90%. 

Mandelic acid, ethyl esters of substituted, cy-cloamylose action on hydrolysis of, 23 233... 

A DKR process was used for the synthesis of (R)-mandelic acid ester from racemic mandelic acid using an aqueous/organic two-phase system with two enzymes. KR first took place with a lipase in the organic solvent and there was an in situ racemization in the aqueous medium by recombinant mandelate racemase. The procedure employed a hollow-fibre membrane bioreactor and gave (R)-mandehc acid ethyl ester in 98% ee and 65% yield (Scheme 4.36) [88]. 

A. Ethyl mandelale. To 152 g. (1.0 mole) of mandelic acid and 200 ml. of absolute ethanol in a 1-1. round-bottomed flask f< ui[)ped with a reflux condenser, there is added 100 ml. of abso-liile ethanol containing about 10 g. of anhydrous hydrogen chlo-lidc (Note 1). The solution is heated under reflux on a steam bath for 5 hours, then poured into 11. of ice water in a 3-1. beaker (Note 2). A saturated aqueous solution of sodium bicarbonate is added until the mixture is faintly alkaline (Note 3). It is I lien extracted with two 300-ml. portions of ether in a 2-1. separatory funnel. The ether extracts are washed with a 200-ml. por-lioii of water and dried over 50 g. of anhydrous sodium sulfate. The dried ether solution is concentrated by distillation from a 25()-ml. Claisen flask, and the residue is distilled at reduced pressure. I here is obtained 147-154 g. (82-86%) of ethyl mandel-iilc, l).p. 144-145°/16 mm. The ester may crystallize upon standing for a prolonged period. It melts at 30.5-31.5°. 

Mandelamide has been prepared by treating the ethyl ester with concentrated aqueous ammonia,12 and a saturated alcoholic solution of ammonia has been used to effect ammonolysis of the methyl ester.1 3 Esters of mandelic acid were treated with liquid... 

Pemoline Pemoline, 2-amino-5-phenyl-2-oxazolin-4-one (8.1.2.7), is synthesized by the condensation of the ethyl ester of mandelic acid with guanidine [13,14]. 

One Sanofi synthesis of enantiomerically pure (-i-)-clopidogrel (2) utilized optically pure (R)-(2-chloro-phenyl)-hydroxy-acetic acid (20), a mandelic acid derivative, available from a chiral pool. After formation of methyl ester 21, tosylation of (/ )-21 using toluene sulfonyl chloride led to a-tolenesulfonate ester 22. Subsequently, the Sn2 displacement of 22 with thieno[3,2-c]pyridine (8) then constructed (-i-)-clopidogrel (2). Another Sanofi synthesis of enantiomerically pure (-i-)-clopidogrel (2) took advantage of resolution of racemic a-amino acid 23 to access (S)-23. The methyl ester 24 was prepared by treatment of (S)-23 with thionyl chloride and methanol. Subsequent Sn2 displacement of (2-thienyl)-ethyl para-toluene-sulfonate (25) assembled amine 26. 

Acetyl mandelic acid was described by Naquet and Lougui-nine,1 but their product has been shown to be contaminated with the ethyl ester of acetyl mandelic acid. Dupont2 obtained the compound by the oxidation of diacetyl 1, 4-diphenylbutine-2-diol-i, 4. Anschutz and Bocker3 prepared acetyl mandelic acid, and from it the acid chloride, by the use of phosphorus pentachloride, but with poor yields. Von Braun and Muller 4 state that acetyl mandelyl chloride can be made from acetylated mandelic acid and thionyl chloride, the resulting product being a viscous yellow oil. 

Microwave irradiation of a mixture of an acid anhydride, an amine adsorbed on silica gel, and TaCl5/Si02 is a solvent-free method for the synthesis of A-alkyl and A-aryl-imides [47]. Ni(II) promotes the conversion of an acrylamide to ethyl acrylate via a Diels-Alder adduct with (2-pyridyl)anthracene [48], Aromatic carboxylic acids [49] and mandelic acid [50] are efficiently esterified with Fc2(S04)3 XH2O as catalyst. Co(II) perchlorate in MeOH catalyzes the methanolysis of acetyl imidazole and acetyl pyrazole [51]. Hiyama et al. used FeCb as a catalyst for the acylation of a silylated cyanohydrin. The resulting ester was then cyclized to 4-amino-2(5H)-furanones (Sch. 5) [52]. 

Problem 21.6 (a) Suggest a mechanism for the base-catalyzed racemization of the optically active ester, ethyl mandelate, C6H3CHOHCOOC2H5. (b) How do you account for the fact that optically active mandelic acid undergoes racemization in base much more slowly than the ester (Hint See Sec. 18.20.) (c) What would you predict about the rate of base-catalyzed racemization of a-methylmandelic acid, C6HsC(CH3)(OH)COOH ... 

Quizalofop ethyl ester 3258 Racemic mandelic acid 2308... 

C2-homologizati on of sugars with, 264-265 Acetamide, JV-bromo- (AcNHBr, NBA) bromohydrination with, 275-276, 287 Acetaminophen (= paracetamol), 301 Acetate, piperidinium cat. for aldol add., 82 —, sodium a-epimerization of ketones, 277 opening of oxiranes, 282 Acetic acid, anhydride (AcfO) protection with. See Protection Pummerer rearr. with, 51, 265 —, esters (See also Protection of hydroxy groups) C-H acidity, 10 1-methylethenyi ester pr., 174 transenolization, 58 —, bromo-, esters pr., 179 a2-synthon, 19, 65, 309 d2-synthon, 19, 301 —, chloro-, esters pr., 179 hydantoins from, 308 —, cyano-, esters pr., 177 pyrrolines from, 298 —, (dialkoxyphosphinyl)-, esters pr 188 Wittig-Horner olefinations, 267, 282 —, diazo-, ethyl ester pr, 176, 178 cyclopropanes from, 74—75 —, dichloro- deblocking of pixyl ethers, 342 —, hydroxy-, esters pr., 176 —, hydroxyphenyl-, (S)- (l-mandelic acid) ... 

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