Hydroxyalkanoate methyl ester

Cao, Q. and Zhang, J. (2112) 3-hydroxyalkanoate methyl esters as Alzheimer disease dmgs. 13th International Symposium on Biopolymers ISBP2012, Cairns, Queensland (Australia). 

Zhang, X.J., Luo, R.C., Wang, Z., Deng, Y., and Chen, G.Q. (2009) Application of (i )-3-hydroxyalkanoate methyl esters derived from microbial poly-hydroxyalkanoates as novel biofuels. Biomacromolecules, 10, 707-711. 

Figure 16.8 Polyhydroxyalkanoates (PHA) can be produced from activated sludge generated from wastewater treatments. PHA-based biofuels including 3-hydroxybutyrate methyl ester (3HBME) and 3-hydroxyalkanoate methyl esters (3HAME) can also be formed from methyl-esterifying PHA. ...

Zhang XJ, Luo RC,Wang Z, DengY, Chen GQ. Applications of (R)-3-hydroxyalkanoate methyl esters derived from microbial polyhydrox kanoates as novel biofuel. Biomacromolecules 2009 10 707-11. 

Figure 15.7 Cliromatographic separation of cliiral hydroxy acids from Pseudomonas aeruginosa without (a) and with (h) co-injection of racemic standards. Peak identification is as follows 1, 3-hydroxy decanoic acid, methyl ester 2, 3-hydroxy dodecanoic acid, methyl ester 3, 2-hydroxy dodecanoic acid, methyl ester. Adapted from Journal of High Resolution Chromatography, 18, A. Kaunzinger et al., Stereo differentiation and simultaneous analysis of 2- and 3-hydroxyalkanoic acids from hiomemhranes hy multidimensional gas cliromatog-raphy , pp. 191 -193, 1995, with permission from Wiley-VCH. (continuedp. 419)...

An alternative to the extraction of intact PHA polymer is the isolation of PHA monomers, oligomers, or various derivatives such as esters [74]. PH As are composed of stereo-chemically pure P-3-hydroxyacids, and therefore can be used as a source of optically pure organic substrates for the chemical and pharmaceutical industry [79]. In this protocol, the defatted cake containing PHA polymer would be chemically treated to obtain the PHA derivatives. For example, transesterification of the meal with methanol would give rise to methyl esters of 3-hydroxyalkanoic acids. The PHA derivatives would then be separated from the meal with appropriate solvents. One potential disadvantage of this method is the potential alteration of the quality of the residual meal if the harsh chemical treatments required for the production of PHA derivatives lead to protein or amino acid breakdown. 

Various enantiomerically pure (/ )-3-hydroxyalkanoic acids (RHA) can be conveniently prepared by depolymerizing the biosynthesized PHA. De Roo et al. (2002) produced the chiral RHA and RHA methyl esters via hydrolytic degradation of PHA synthesized by pseudomonads. They first hydrolyzed the recovered PHA by acid methanolysis and then distilled the RHA methyl ester mixture into several fractions. Subsequently, the RHA methyl esters were saponified to yield the corresponding RHA with final yields of the RHA up to 92.8% (w/w). 

A large-scale cyclization reaction of carbamates with functionalized butenoates, starting from carbamates prepared without phosgene, for the efEdent preparation of 3-(substituted phenyl)-5-isopropylidene-l,3-oxazolidine-2,4-dione derivatives (azaladones) having potent herbicidal adivity, has been described in a patent application [240]. By reacting an N-(substituted phenyl)carbamate 312 with a 2-hydroxy-3-alkenoic acid ester (for example, ethyl 2-hydroxy-3-methyl-3-butenoate) or a 3-alkoxy-2-hydroxyalkanoic add ester, at 210 °C for 15 h, azaladone 313 was formed in 71.5% yield. 

By simply hydrolyzing the easily accessible 2-hydroxy-2-methylalkanenitriles with concentrated acid, 2-hydroxy-2-methylalkanoic acids are obtained without measurable racemization (Table 3). The reaction sequence from the starting ketone to the carboxylic acid can be carried out in one pot without isolation of the cyanohydrin. The enantiomeric excesses of the (/ )-cyanohydrins and the (ft)-2-hydroxyalkanoic acids are determined from the ( + )-(/T)-Mosher ester derivatives and as methyl alkanoates by capillary GC, respectively. The most efficient catalysis by (R)-oxynitrilase is observed for the reaction of hydrocyanic acid with 2-alkanoncs. 3-Alkanoncs are also substrates for (ft)-oxynitrilase, to give the corresponding (/ )-cyanohydrins32. 

The methyl 3-hydroxyalkanoates can be transformed into optically pure compounds. Thus, the esters were hydrolyzed to the corresponding acids, and the dicyclohexyl ammonium salts were recrystallizcd from acetonitrile. Three recrystallizations gave the optically pure 3-hydroxyalka-noic acids in 50-75% yield67. In some cases, the dibenzyl ammonium salts were superior to the dicyclohexyl ammonium salts, e g., for 3-hydroxybutanoic acid, which was obtained optically pure after two recrystallizations from acetonitrile68. 

---