Hydroxycarboxylic acids 3-hydroxy esters

Methyl esters of unsaturated acids (loss of CH3OH + HzO) Methyl esters of straight-chain hydroxycarboxylic acids except 2-hydroxy acids... 

The application of RCM to dihydropyran synthesis includes a route to 2,2-disubstituted derivatives from a-hydroxycarboxylic acids. In a one-pot reaction, the hydroxy esters undergo sequential O-allylation, a Wittig rearrangement and a second O-allylation to form allyl homoallyl ethers 8. A single RCM then yields the 3,6-dihydro-2//-pyran 9. The process is readily adapted not only to variably substituted dihydropyrans but also to 2-dihydrofuranyl and 2-tetrahydrooxepinyl derivatives and to spirocycles e.g. 10 through a double RCM (Scheme 4) <00JCS(P1)2916>. 

For utility of optically active /3-hydroxy esters D. Seebach, S. Roggo, and J. Zimmermann, Biological-Chemical Preparation of 3-Hydroxycarboxylic Acids and Their Use in EPC-Syntheses, in W. Bartmann and K. B. Sharpless, eds., Stereochemistry of Organic and Bioorganic Transformations, p. 85, Verlag Chemie, Weinheim, 1987. 

Reformatsky reaction -b-hydroxy acids [HYDROXYCARBOXYLIC ACIDS] (Vol 13) -use of bromoacetic esters [ACETIC ACID AND DERIVATIVES - HALOGENATED DERIVATIVES] (Vol 1)... 

Combination of the coordinating ability of metal ions for hydroxy group containing compounds with the before mentioned exceptional behaviours of DBTA in chiral recognation processes gave us a new possibility for direct resolution of a-alkoxycarboxylic acids, a-hydroxycarboxylic acid esters and series of racemic alcohols... 

Fig. 13.40. Alkylation of an ester enolate for the preparation of an a-hydroxycarboxylic acid (for the preparation of enantiomerically pure a-hydroxy carboxylic acid through alkylation of an enantiomerically pure ester enolate cf. Figure 13.41). The initially formed benzyl ester B contains two benzylic C—0 bonds, which can be cleaved by means of hydrogenolysis.

Ester reduction. A method for the conversion of dicarboxylic acids to CD-hydroxycarboxylic acids involves formation and reduction (with NaBH ) of dilactones in which the two carbonyl residues are linked by tm OCH2O chain. Arylpyruvic esters can be reduced to either the a-hydroxy esters or 1,2-diols. ... 

Polyesters contain the ester group —COO— in the main chain. Many methods are suitable for their synthesis self-condensation of a,o>-hydroxy acids, ring-opening polymerization of lactones, the polycondensation of dicarboxylic acids with diols, transesterification, the polycondensation of diacyl chlorides with diols, polymerization of O-carboxy anhydrides of a- and jS-hydroxycarboxylic acids, and the copolymerization of acid anhydrides with cyclic ethers. The last reaction is commercially used in the curing of epoxides with anhydrides. 

Hydroxycarboxylic acid esters (s. a. / -Hydroxy-y,6--acetylenecarboxylic acid esters)... 

Cyclic ethers react faster than alicyclic ones [347, 348, 553]. Highly reactive are epoxides. Their reaction products — hydroxycarboxylic acids or the corresponding esters — react to give unsaturated acids or esters by dehydration. Under mild conditions the hydroxyesters can be isolated as such. McClure reported a 53 % yield of 4-chloro-3-hydroxy butyrate obtained in the carbonylation of epichlorohydrin [1023]. 

Hydroxycarboxylic acids and 5-hydroxycarboxylic acids occur in the form of corresponding y- and 5-lactones in many fruits, especially apricots and peaches. Many other hydroxy fatty acids are also found in seed oils of plants. For example, (S)-jalapinolic acid (3-28) occurs in lipophilic ester-type dimers of acylated pentasaccharides derived from L-rhamnose in sweet potato Ipomoea batatas, Convolvulaceae), which are known as batatins. (9Z,12S)-12-Hydroxyoctadec-9-enoic (ricinoleic) acid (3-29) occurs in castor oil, where it represents about 90% of the total fatty acids. So-called castor oil is extracted from the seeds of the castor oil plant Ricinus communis) of the Euphorbiaceae family, and is used only for technical purposes as it has purgative properties. 

An aldol addition in present-day terminology involves the addition of the a-C atom of a carbonyl compound, a carboxylic acid, a carboxylic ester, or a carboxylic amide to the C=0 double bond of an aldehyde or a ketone. In the past, the term aldol addition was used in a more restricted sense, referring to the addition of the a-C atom of nothing but carbonyl compounds to the C=0 double bond of aldehydes and ketones. The products of aldol additions in today s usage of the term are (i-hydroxy Icarbonyl compounds (aldols), (i-hydroxy carboxylic acids, /3-hydroxycar-boxylic esters, or /3-hydroxycarboxylic amides. 

DIASTEREOSELECTIVE a-ALKYLATION OF g-HYDROXYCARBOXYLIC ESTERS THR0U6H ALKOXIDE ENOLATES (+)-DIETHYL (2S,3R)-3-ALLYL-2-HYDROXYSUCCIMATE FROM (-)-DIETHYL S-MALATE (Butanedlolc acid, 2-hydroxy-3-(2-propenyl)-, diethyl ester, [S-(R,S)])... 

---