Ethyl -mandelate

If RCOOH is a comparatively simple organic acid and R OH a monohydric alcohol then the enzyme is called an esterase. Examples of such esters are ethyl butyrate, C3H7COOC2H5, and ethyl mandelate, CeHjCH(OH)COOC2Hj. 

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°. 

Chlorophenylacetic acid has been prepared from mandeloni-trile and hydrochloric acid in a sealed tube, from mandelic acid and hydrochloric acid in a sealed tube/ from a-nitrostyrene and hydrochloric acid in a sealed tube, from phenylglycine, hydrochloric acid, and sodium nitrite, from mandelic acid and phosphorus pentachloride (to give the acid chloride which is then hydrolyzed), and, in poor yield, from mandelic acid and thionyl chloride. In the method described, ethyl mandelate is prepared according to Fischer and Speier. The conversion to the chloroester and the acid hydrolysis step are modifications of a preparation described by McKenzie and Barrow. ... 

Certain classes of compounds are too reactive for the present method. Ethyl mandelate produced a racemic, protected phenyl glycine derivative. Benzylic alcohols with two methoxy groups (directly conjugating in the 2 and 4 positions) gave azide of 50% e.e. 

The results collected in Table 5 suggest that hydrocarbon residues, especially aromatic groups, in the solvent are strongly responsible for the interaction with cis-(1+4). The position of the largest hydrocarbon residue apparently determines whether P- or M-[6]-helicene will be formed in excess. Replacement of the methyl group in (S)-ethyl lactate (b) by a phenyl group giving (S)-ethyl mandelate (d), increases the optical yield fivefold. 

The dimethylaminooxazolidone derivative thozalinone (40-3) is described as an antidepressant. The synthesis of this agent again uses a cyanamide, provided in this case as a preformed reagent. Thus, reaction of alkoxide from ethyl mandelate (40-1) with A,A-dimethylcyanamide leads to the amidine (40-2) by addition to the nitrile. Internal displacement of the ester ethoxide group closes the ring to an oxazo-lidinone, forming the product (40-3) [42]. 

Hydrolase Resolution of (R,S)-ethyl mandelate and (R,S)-ethyl 2-chloromandelate in phosphate buffer / iso-octane [68, 69]... 

In the same study, redox polymers (223) were prepared that contained pendant viologens (Scheme 108). An active reducing agent was obtained by chemical reduction with dithionite or zinc, electrochemically, or by exposure to light. Utilization of the reduced poly(viologen) (224) as an electron transfer mediator was demonstrated by addition of a catalytic amount of the polymer to a mixture of zinc powder, ethyl benzoylformate (225) and water-acetonitrile (1 5). A quantitative yield of ethyl mandelate (226) was obtained after two days at room temperature (Scheme 109). Without the polymer, no reaction was observed after a month. 

This method has been used for the preparation of numerous amides.2 However, with many esters it is necessary to heat the reaction mixture to 200-250° for a few hours. Ethyl mandelate is like ethyl lactate in that it gives a good yield (75-80 per cent of the theoretical amount) of mandelamide at room temperatures. 

Methyl phenoxyacetate Ethyl phenoxyacetate Ethyl ( + )-mandelate Methyl ( + )-mandelate... 

Charge an oven-dried single-necked round-bottomed flask possessing a side-arm stopcock (100 mL) with ketenylidenetriphenylphosphorane (3.0 g, 10 mmol), ethyl mandelate (0.94 g, 8 mmol), dry toluene (75 mL), and a magnetic stirrer bar. Equip the flask with a reflux condenser fitted with a mercury float valve (or a septum/balloon combination). Flush the entire... 

Ethyl isocyamde, 35, 62 Ethyl isodehydroacetate, 32, 76 Ethyl lactate, 31, 59, 60 Ethylmagnesium bromide, 36, 87 Ethyl mandelate, 36, 3 Ethyl N-methylcarbamate, 35, 94 /S-ElHYL-iS-METHYLGLUTARIC ACID, 36, 28... 

H. lUhyl a-chlorophenylacetate. Ethyl mandelate (135 g., 0.75 mole) is dissolved in 98 g. (59 ml., 0.82 mole) of thionyl chloride (Note 4) contained in a 500-ml. round-bottomed flask equipped with a rellux condenser capped with a drying tube. The apparatus is allowed to stand in a hood overnight (about 16 hours), at the end of which time the solution is heated under reflux for... 

Related Reagents. (S)-Ethyl Lactate Ethyl Mandelate 3-Hydroxyisobomeol. 

Under similar conditions but with different oxidants, esters are hy-droxylated in the a positions with respect to the ester groups. Ethyl phen-ylacetate in tetrahydrofuran treated with lithium diisopropyl amide at -78 °C followed by oxidation with molybdenum oxide complex gives ethyl mandelate in 58% isolated yield [531]. Another way to obtain a-hydrox-ylated (or methoxylated) esters is by oxidation with iodobenzene diacetate in the presence of potassium hydroxide (or sodium methoxide) (equation 466) [794]. 

Attempts to achieve optical induction during the reduction of aromatic ketones to the secondary alcohol with the help of a single layer of chiral catalyst covalently attached to a graphite cathode have been much less successful. Reduction of 4-acetylpyridine at a graphite surface coated with (S)-phenylalanine methyl ester afforded an enantiomeric excess of the (S)-pyridinylethanol. In other experiments, ethyl glyoxylate afforded ethyl (—)-mandelate with 9.7% enantiomeric excess [101]. Results using such modified surfaces have, however, proved highly irreproducible [102]. 

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 ... 

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