Lactic acid, derivative

In view of the ready availabiUty of optically pure lactic acid derivatives this reaction offers an attractive general method for the preparation of optically pure aromatic ester derivatives (41). Stereoselective alkylation (15—60% inversion) of ben2ene with optically active 1,2- 1,3- and 1,5-dihaloalkanes was also reported (42). 

The fermentation-derived food-grade product is sold in 50, 80, and 88% concentrations the other grades are available in 50 and 88% concentrations. The food-grade product meets the Vood Chemicals Codex III and the pharmaceutical grade meets the FCC and the United States Pharmacopoeia XK specifications (7). Other lactic acid derivatives such as salts and esters are also available in weU-estabhshed product specifications. Standard analytical methods such as titration and Hquid chromatography can be used to determine lactic acid, and other gravimetric and specific tests are used to detect impurities for the product specifications. A standard titration method neutralizes the acid with sodium hydroxide and then back-titrates the acid. An older standard quantitative method for determination of lactic acid was based on oxidation by potassium permanganate to acetaldehyde, which is absorbed in sodium bisulfite and titrated iodometricaHy. 

Lactic-acid-based polymers, synthesis methods for preparing, 20 298 Lactic acid derivatives, 14 124 Lactic acid polymers, 14 125-126 Lactide (LA). See also Lactic acid entries early attempts to polymerize, 20 299 high purity, 14 123... 

N. Seurre, K. Le Barbu Debus, F. Lahmani, A. Zehnacker Rentien, N. Borho, and M. A. Suhm, Chiral recognition between lactic acid derivatives and an aromatic alcohol in a supersonic expansion Electronic and vibrational spectroscopy. Phys. Chem. Chem. Phys. 8, 1007 1016 (2006). 

By enantiotopos-differentiating deprotonation the lithiated complex is formed in a reagent-controlled reaction with excellent selectivity. The lithiated center of the complex is assumed to have the S configuration, as follows from the carboxylation, to give an (7 )-lactic acid derivative based on the reasonable assumption of metalloretentive electrophilic attack. Trapping with chlorotrimethylstannane gave the corresponding chiral (.S -SjS-dimethyl-l-trimethylstannyl-alkyl-l-oxa-4-azaspiro[4.5]decane-4-carboxylates. Enantioselectivity of the overall transformation is excellent. 

Datta,R., Tsai, S. R,Bonsignor, R,Moon, S., Frank, J. (1995). Technological and economic potential ofpoly(lactic acid) and lactic acid derivatives. FEMSMicrobiol. Rev, 16, 221-231. 

Especially high optical inductions have been achieved with catalysts which contain BPPM (13), PPM (14) or (15) as chiral ligands. Pyruvic acid esters were usually hydrogenated to lactic acid esters in quantitative chemical yield with an enantiomeric excess of 65-75%41 a,53). However, this method is not of technical significance, since chiral lactic acid derivatives may be produced more conveniently by biotechnological processes. 

In addition to the more or less popular methods of depsipeptide synthesis discussed vide supra, there are also a limited number of complementary and effective synthetic procedures that have been described for this purpose. Among these, the well-known method of symmetric anhydrides from N-protected amino acids has to be considered. This method has found successful use in the esterification of hydroxy acids in the presence of some catalyst additives. Initially, the addition of pyridine11091 or 1-hydroxybenzotriazole in pyridine1 101 to a symmetric anhydride was utilized for ester bond formation. As an example, Katakai has prepared a number of didepsipeptides in 85-96% yield by means of a 2-nitrophenylsulfenyl /V-carboxy anhydride with lactic acid derivatives in the presence of pyridine.1 09 ... 

Ethyl lactate is another lactic acid derivative that has recently been commercialized. An environmentally benign solvent with properties superior to many conventional petroleum-based solvents, it can be blended with methyl soyate derived from soybean oil to create custom-tailored solvents for various applications. 

Culture medium needs to be buffered to compensate for CO2 and lactic acid derived from glucose metabolism. Most culture media employed for animal cells are buffered with CO2 originating from the gaseous phase, in equilibrium with sodium bicarbonate (NaHCCF) added to the culture medium, as described by the following equilibrium reaction ... 

High molecular weight perfluorinated tertiary alcohols can be prepared by the reaction of (perfluoroalkyl)- and (perfluorooxaalkyl)trimethylsilanes with fluoro ketones (vide supra). The reaction has been extended to carbonyl compounds other than ketones acid fluorides gave ketones, but no reaction was observed with esters. a-Oxo esters react with trimethyl(tri-fluoromcthyl)silane with fluoride initiation in tetrahydrofuran /(./(. -trifluoro lactic acid derivatives are produced in good yields in one step. 

Several lactic acid derivatives were used by Gessner et al. for the determination of the enantiomeric purity of flavor substances such as chiral alcohols from natural sources. Diastereomeric 0-acetyl-, propionyl-, and hexanoyllactic acid esters of the chiral alcohols were separated by GLC (155). A report from the same laboratories described characterization of several chiral aroma substances that are S-lactones. The lactones were hydrolyzed to the corresponding hydroxy acids, and the acid moiety was esterified to the isopropyl ester. The remaining hydroxyl group was esterified with (R)-2-phenylpropionic add chloride or [30], and the diastereomeric derivatives were separated using preparative silica gel LC. The derivatives were also separated on an analytical scale by GLC (156). 

Vauthier, C. Schmidt, C. Couvreur, P. Measurement of the density of polymeric nanoparticulate drug carriers made of poly(alkylcyanoacrylate) and poly(lactic acid) derivatives. J. Nanoparticle Res. 1999, 1, 411-418. 

One of the most highly developed biopolymers is poly (lactic acid) (PLA). In the USA, PLA is manufactured by NatureWorks at a plant in Nebraska using lactic acid derived from corn. (Lactic acid can also be obtained from other natural sources such as wheat or potatoes.) Poly (lactic acid) is produced by ring opening polymerization of the lactide, as shown in Figure 8.12. 

Photocyclization using circular polarized light yielded dihydro[5]helicene in a small enantiomeric excess (ee = 3 %). Attempts were also made to enantioselectively synthesize helicenes using chiral solvents as well as cholesteric liquid crystals Excellent enantiomeric excesses (up to 98%) were obtained through temporary introduction of optically active residues like mandelic acid, lactic acid derivatives and (—)-menthyl esters... 

Lactic acidosis is one of the most common canses of high SAG metabolic acidosis. Lactic acid is the end prodnct of anaerobic metabolism of glucose (glycolysis). In normal individnals, lactic acid derived from pyruvate enters the circulation in small amonnts and is promptly removed by the liver. In the liver, and to a lesser extent in the kidney, lactic acid is reoxidized to pyruvic acid, which is then metabolized to CO2 and H2O. The normal plasma lactate concentration in healthy subjects is approximately 1 rnEq/L. " The diagnosis of lactic acidosis should be considered in aU patients with metabolic acidosis... 

PLA An important feature of the lactic acid is its ability to exist in two optically active forms l- and D-isomers. Lactic acid derived from fermentation consists of 99.5% L-isomer and 0.5% o-isomer. The production of the cyclic lactide dimer intermediates results in three potential l-, d-, and l/d (wso)-forms and a racemic equal mixture of d- and L-forms. The l- and o-forms are optically active while the meso-foxm and the racemic mixture are optically inactive (Fig. 2). 

In order to meet market requirements, it is necessary to produce high optical purity lactic acid derivatives (greater than 99.5%). 

R)- and (S)-2-Phenyl-l,4-butancdiol (21 and 22) have been prepared from (5)-lactic acid derivatives by the following reaction sequence392. 

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