L-malic acid

L-Malic acid [97-67-6] M 134.1, m 104.5-106 , [ajp -2.3 (c 8.5, HjO), pK, 3.46, pK 5.10. Crystd (charcoal) from ethyl acetate/pet ether (b 55-56°), keeping the temperature below 65°. Or, dissolved by refluxing in fifteen parts of anhydrous diethyl ether, decanted, concentrated to one-third volume and crystd at 0°, repeatedly to constant melting point. 

The protein polymers are highly sterospecific, the aminoacid residues always adopting the L-configuration, i.e. the same configuration as the reference substance L-malic acid. 

Fumaric acid is converted to L-malic acid by hydration in the presence of the enzyme fumamse. From the structure of the substrate and the configuration of the product, it is apparent that the hydroxyl group has been added to the si fiice of one of the carbon atoms of the double bond. Each of the trigonal carbon atoms of an alkene has its fiice specified separately. The molecule of fumaric acid shown below is viewed fixjm the re-re fiice. 

Poly(L-malic acid) denotes a family of polyesters derived from L-malic acid as the building unit. By chemical synthesis, three kinds of poly(L-malic acid) have been obtained, depending on the molecular position of the ester bond the a-type(I) [1], the j8-type(II) [2], and the a,j8-mixed-type(III) [3). 

The following chapters will be devoted to the production of j8-poly(L-malic acid) or its salt by fermentation, its Isolation, and physico-chemical characterization. The biosynthesis, degradation, and presumed physiological role will be also considered. 

The first organism reported to produce poly(L-malic acid) was Penicillium cyclopium [7]. An amount of 2.6-... 

The strongest known producer of j8-poly(L-malic acid) has been identified as Aureobasidium sp. providing 61 g of polymer from 1 liter of culture medium [5,6]. 8-Poly(L-malate, Ca -salt) of the culture broth was first separated from accompanying bulk pullulan by methanol precipitation. The water-redisolved precipitate was converted to the polymer acid by passage over Amberlite IR-120B (H -form). Thus, the best to-day producers of... 

The purification of j8-poly(L-malic acid) from A o-basiae has been reported involving methanol precipitation of the polymer in the form of the Ca salt [5]. This is possible because a high concentration of CaCOs is present in the growth medium. Unfortunately, the polymer acid is not soluble in aceton thus missing an additional purification step. In our hands, purification of jS-poly(L-malate) from several Aureobasidiae strains was unsatisfactory because of low yields and resisting impurities. 

Table 1 Purification of /3-Poly(L-Malic Acid) and Its Potassium Salt from the Culture Medium of Plasmodia of Physarum polycephalum...

Obtain free -poly(L-malic acid) after passage over Amberlite IR 120 (H -form) (20 ml bed volume/1 g of polymer salt). Lyophylize, dissolve powder in acetone, remove insoluble material by centrifugation, and evaporate acetone from the supernatant. 

S-Poly(L-malic acid) ionizes readily in water giving rise to a highly soluble polyanion. Thus, a 2% solution of the free acid of the polymer from Aureobasidium sp. A-91 showed a pH 2.0 [5]. The ionic constants have been determined to be pKa = 3.6 for the polymer from Aureo-basidumsp. A-9 [5] and pKa (25°C) = 3.45 for/3-poly(L-malic acid) of Mw 24 kDa from F. polycephalum (Valussi and Cesaro, unpublished results) Thus, the polymer is highly charged under physiological conditions (pH 7.0). 

The assay as above was used containing 1.5 g/ml /3-poly(L-malic acid) (9.6 mM in terms of malyl residues). 

Substantial amounts of polymalatase have been isolated from plasmodial extracts. This may refer to stored enzyme before secretion, because /3-poly(L-malate) is not degraded in plasmodia [24]. Several other fungi were found to secrete /3-poly(L-malate) degrading activities to L-malic acid (Ratberger, Molitoris and Holler, unpublished results). These enzymes have not yet been purified and characterized. 

Scheme 9). Although cyanohydrin acetonide 64 could conceivably have been used, the silyl ether 75 was chosen. This compound is readily available from (l)-malic acid, and can undergo electrophilic activation under far more mild conditions than compound 64. Alkylation of the 1,3-diol synthon 75 with bromide 76 created the C11-C26 framework of roflamycoin, in 85% yield. A two-step conversion of the terminal siloxy group to the primary iodide (78) proceeded in 80% overall yield. 

Enantioenriched (-)-rosmarinecine, which belongs to the group of pyrrolizidine alkaloids [413], has been synthesized by Goti, Brandi and coworkers applying an intramolecular 1,3-dipolar cycloaddition as the key step [414]. The required nitrone was obtained in situ from L-malic acid. Moreover, 1,3-dienes as precursors for a cy-... 

Danneel, H.J., Busse, M. and Faurie, R. (1995) Pharmaceutical grade L-malic acid from fumaric acid -development of an integrated biotransformation and product purification process. Mededlingen van de Faculteit Landbouwwetenschappen, Rijksuniversiteit te Gent, 60 (4a), 2093—2096. 

The enantiomerically pure indolizidine (—)-422 has been synthesized starting from L-malic acid diethyl ester 407. The hydroxyl function of L-malic acid diethyl ester 407 has been protected as dihydropyranyl ether 408 with 2/7-dihydropyran and Amberlyst 15 in pentane at room temperature. The diethyl ester 408 was then reduced with lithium aluminium hydride in diethyl ether under reflux and the newly generated hydroxyl functions then protected with mesyl chloride in the presence of triethylamine in dichloromethane at 0°C. This was converted into newly protected pyrroline nitrone 409 in 44% overall yield through a well-established method (Scheme 90). The regio-isomeric 5-pyrroline-iV-oxide 410 formed in 4% overall yield was easily separated by column chromatography <20000L2475>. 

Poly-j3-malate is readily degraded completely to L-malic acid under both acid and base conditions [108], and it can also be hydrolyzed by enzymes within the cell [105,106]. Recently, several bacteria were isolated which were able to utilize poly-/i-malate as sole carbon source for growth [109]. Because the polymer is biodegradable and bioadsorbable, it is of considerable interest for pharmaceutical applications, especially in controlled-release drug delivery systems [97,98]. Chemical routes to poly-/ -malate are expected to provide materials with various properties [110]. 

Extracellular, exo-type poly(/3-L-malic acid) hydrolase 124... 

Naouri, P., Bemet, N., Chagnaud, P., Amaud, A., and Galzy, P., Bioconversion of L-Malic Acid into L-Lactic Acid Using a High Compacting Multiphasic Reactor (HCMR), J. Chem. Tech. Biotechnol., 51 81 (1991)... 

When an atom or group directly linked to an asymmetric carbon atom is replaced, the configuration of the new compound may be opposite to that of the original. Thus L(-) malic acid can be converted into D-(+) malic acid as follows ... 

D (-) malic acid L (+) chloro succinic acid L (+) malic acid... 

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