Pantothenic hydroxy

The process of racemization has a number of practical application in the laboratory and in industry. Thus, in the synthesis of an optical isomer it is frequently possible to racemize the unwanted isomer and to separate additional quantities of the desired isomer. By repeating this process a number of times it is theoretically possible to approach a 100% yield of Synthetic product consisting of only one optical isomer, An example of the utilization of such a process is found in the production of pantothenic acid and its salts, In this process the mixture of D- and L-2-hydroxy-3,3-butyrolactones are separated. The D-lactone is condensed with the salt of beta-alanine to give the biologically active salt of pantothenic acid, The remaining L-lactone is racemized and recycled. 

Pantolactone, dihydro-3-hydroxy-4//-dimethyl-2(3//)-furanone (103) which is an important starting material of the synthesis of pantothenic acid, was also easily resolved by complexation with 10a. When a solution of 10a (5.5 g, 9.93 mmol) and rac-103 (2.6 g, 20 mmol) in 1 1 benzene-hexane (20 ml) was kept at room temperature for 1 h, a 1 1 complex of 10a and (.S)-(-)- 03 was obtained, after two recrystallizations from 1 1 benzene-hexane, as colorless needles (2.05 g), which upon heating in vacuo gave (S)-(-)-103 of 99% ee (0.39 g, 30%).40 In order to clarify the mechanism of the precise chiral recognition between 10a and (S)-(-)-103, their inclusion complex crystal was studied by X-ray analysis40 and by AFM technique.41... 

The development of a novel production system for D-pantoyl lactone (which is a lactone compound carrying a chiral hydroxy group and a chiral intermediate for the commercial production of D-pantothenate) by microbial asymmetric reduction has been undertaken. D-pantothenate is mainly used in various pharmaceutical products and as an animal feed additive, the current world production of calcium pantothenate being about 6,000 tons per year. Conventional commercial production of D-pantoyl lactone has depended exclusively on chemical synthesis involving optical resolution of a chemically synthesized racemic pantoyl lactone, which is the most troublesome step of the pantothenate synthesis process. 

Dihydroxyacid dehydratase (E.C. 4.2.1.9) is a ubiquitous enzyme that is involved in the biosynthesis of the branched-chain amino acids (lie, Leu and Val) and of pantothenic acid and coenzyme A. The enzyme catalyzes the elimination of water from 2,3-dihydroxyalkanoic acids (23) to 2-hydroxy-2-alkenoic acids (24), which tautomerize to 2-ketoalkanoic acids (25). The enzyme from spinach has the highest activity towards 2,3-dihydroxy-3-methylbutanoic acid (Val precursor, Scheme 11.5-4) but also accepts other substrates1341. Thus, 2,3-dihydroxybutanoic acid, 3-cyclopropyl-2,3-dihydroxybutanoic add as well as 2,3-dihydroxy-3-methylpentanoic acid are substrates. With the latter substrate a slight preference for (2R,3S)-2,3-dihydroxy-... 

Dimethyloxolane-2,3-dione (ketopantolactone), which contains an activated keto group, is one of the standard substrates for the enantioselective hydrogenation of carbonyl groups. Its hydrogenation product, 3-hydroxy-4.4-dimethyloxolan-2-one (pantolactone). is a precursor of pantothenic acid, a vitamin B block constituent. 

R ]]-N- 2,4-Dikyd roxy-3,3-dimethyt-I -oxobutyl - -alanine 2-[(dlchloroacetyl)amino]-3-hydroxy-3-(4-nitrophen-ylipropyt ester pantothenic acid ester with 2,2-dichloro-N-[3 hydrOxy-a-(hydroxymethyii-p-nilrophenethylJacetamide ... 

About 6,0001 of the animal feed additive calcium-D-pantothenate are produced annually via D-pantolactone (d-112) (Scheme 35, left side).D-Pantolactone itself is an important chiral intermediate for chemical synthesis and a chiral resolution agent for optically pure amines. Optically pure d-112 is for instance produced by Fuji Chemical Industries by using the D-specific 1,4-lactone hydroxy-acylhydrolase from Fusarium oxysporum [100-102], an enzyme that catalyzes the stereospecific hydrolysis of various kinds of lactones. Treatment of mc-112 leads to an exclusive hydrolysis of d-112 the hydroxy acid d-113 can be easily separated from the remaining lactone l-1 12 and is subsequently chemically con-... 

Pantolactone (PL) [(i )-(-)-3-hydroxy-4,4-dimethyltetrahydofuran-2-on], 1 (Scheme 7.23.), is an intermediate in the preparation of several biologically important molecules such as D-(+)-pantothenic acid, 2, which is a member of B vitamins (Vitamin B5) and is an important constituent of coenz5me A. The biosynthesis of 2 involves the asymmetric reduction of ketopantolactone, i, (KPL) (4,4-dimethyltetrahydrofuran-2,3-dion) to R- -)-PL, because only the 7 -(-)-enantiomer is biologically active. 

Figure 7.6 Biosynthesis of (fi)-pantothenic acid and the side metaboiite 3-(2-hydroxy-3-methyi-butyryiamino)-propionic acid (HMBPA) in B. sub-tilis. Regeneration of methyiene tetrahydrofoiate (THF=CH2) in the GiyA-cataiyzed reaction and in the giycine cieavage cycie (GcvPA, GcvPB, and GcvT) is shown as weii.

A side product, 3-(2-hydroxy-3-methyl-butyrylamino)-propionic acid (HMBPA), can accumulate to high concentrations in the cultivation broth of (7 )-pantothenate-overproducing strains [177]. HMPBA formation is caused by premature a-KIV reduction to 2-hydroxyisovalerate (a-HIV) most probably by PanE before the molecule is hydroxymethylated (Figure 7.6). PanC-catalyzed condensation of a-HIV and P-alanine delivers HMBPA. 

Caicium Pantothenate USP, FCC, Calcium pantothenate. See Calcium D-pantothenate Calcium D-pantothenate CAS 137-08-6 EINECS/ELINCS 205-278-9 Synonyms Calcium d(+)-N-(a,y-dihydroxy-p,p-dimethylbutyryl)-P-alaninate Calcium N-(2,4-dihydroxy-3,3-dimethyl-1-oxobutyl-p-alanine Calcium pantothenate d-Calcium pantothenate Calcium d-pantothenate N-(2,4-Di hydroxy-3,3-di methyl buty ryl-P-alan i ne calcium D-N-(2,4-Dihydroxy-3,3-dimethyl-1-oxobutyl-p-alanine, calcium salt Extro calcium pantothenate Pantothenate calcium Pantothenic acid, calcium salt Vitamin B Vitamin B, calcium salt Definition Calcium salt of pantothenic acid Empirical C19H34N2O10 Ca Properties Wh. powd., odorless, sweetish taste with si. bitter aftertaste stable in air sol. in water, glycerol insol. in alcohol, chloroform, ether m.w. 490.63 m.p. 170-172 C dec. 195-196 C Toxicology LD50 (oral, mouse) 10 g/kg, (IP, rat) 820 mg/kg, (IV, rat) 830 mg/kg mod. toxic by IP, subcut., and IV routes mildly toxic by ing. TSCA listed... 

Urea, (2,5-dioxo-4-imidazolydinyl)-, compd. with N-(3-hydroxymethyl-3-methyl-2-hydroxybutanoyl)-3-aminopropanoic. See Allantoin calcium pantothenate Urea, (2,5-dioxo-4-imidazolydinyl)-, compd. with olean-12-en-29-oic acid, 3p-hydroxy-11-oxo-. See Allantoin glycyrrhetinic acid Urea, (2,5-dioxo-4-imidazolydinyl)-, compd. with 2H-thieno [3,4- d] imidazole-4-pentanoic acid, hexahydro-2-oxo-, [3as-(3aa,4b,6aa)]. See Allantoin biotin... 

The method of choice for the determination of most vitamins is HPLC due to its high separation capability, its mild analytical conditions, and the possibility to use various specifically adapted detection methods, e.g., LTV, fluorescence, or MS detection. All fat-soluble vitamins and most water-soluble vitamins have chromophores suitable for UV detection. Separation of vitamers and stereoisomers can be achieved. If a higher sensitivity is required HPLC with fluorescence detection can be used, either directly (e.g., vitamins A and E) or after derivatization (e.g., thiamine). A further improvement in sensitivity and specificity has been achieved by introducing HPLC with mass spectrometric detection in vitamin analysis. Due to the structural information retrievable, e.g., molecular mass, fragmentation pattern, this is the method of choice for analysis of samples with complex mixtures or low vitamin concentrations. Examples for the use of HPLC-MS in vitamin analysis include the determination of 25-hydroxy-D3 and pantothenic acid. However, one drawback of mass spectrometry is the need for an isotopically labeled reference compound for reliable quantification. Due to the structural complexity of many vitamins, these reference compounds are often expensive and difficult to synthesize. An interesting unique application is the determination of vitamin B12 by HPLC-IPC-MS, which is possible due to its cobalt content. 

An alcohol related to pantothenic acid (and referred to as o-panthenol or D-pantothenyl alcohol) also possesses vitamin activity (Figure 8.7) because it is readily oxidized to form pantothenic acid in organisms. Only o-panthenol is biologically active. The lUPAC name is (27 )-2,4-dihydroxy-iV-(3-hydroxy-propyl)-3,3-dimethylbutanamide and the CAS number is 81-13-0. It is... 

Stiller and associatesin the Merck laboratories a little less than a year after the collaboration began isolated the lactone from concentrates, and determined its structure by classical methods to be -hydroxy-/5,/ -dimethyl-y-butyrolactone. This was synthesized and resolved into its optical isomers. The levo-rotatory lactone when condensed with /3-alanine by various pro-ceduresi >22>2 yields dextro-rotatory pantothenic acid with full biological activity. The antipode was found to be inactive. The biologically active form has, according to Hudson s amide rule, the D-configuration24.2s. 

Hydroxypantothenic acid (Af-( -hydroxy-j8,j8 -dimethylolbutyryl)-/ -alanine) has up to about 20% of the activity of pantothenic acid for some microorganisms. Several other related lactones yielded products with appreciable activityi - i. 

Although there are a number of syntheses of pantothenic acid, that of Folkers et al. is among the earliest. As shown in Scheme 12.108, a clean synthesis of a-hydroxy-P,P-dimethyl-Y-butyrolactone was needed. First, 2-methylpropanal (isobutyraldehyde) underwent an aldol condensation with formaldehyde (formalin, H2C=0) to produce a,a-dimethyl-P-hydroxypropanal. Then, the bisulfite adduct of this aldehyde underwent reaction with potassium cyanide (KCN) and the separated cyanohydrin was hydrolyzed with concentrated hydrochloric acid (HCI), and the product was carefully made basic. The racemic a-hydroxy-P,P-dimethyl-y-butyrolactone was separated, while the lactone underwent ring opening in the... 

Pantothenic acid is a yellowish viscous oily liquid, which is readily soluble in water, alcohols, and dioxane, slightly soluble in diethyl ether and acetone, and virtually insoluble in benzene and chloroform. The stability of pantothenic acid in aqueous solutions is very pH dependent. It is most stable in slightly acidic medium (pH 4 to 5). Both in acidic and alkaline media it is hydrolytically cleaved to yield pantoic acid and its salts, respectively, and P-alanine. In acidic solutions, pantoic acid spontaneously eliminates one molecule of water, forming R)-2-hydroxy-3,3-dimethyl-4-butanolide (a-hydroxy-P,P-dimethyl-y-butyrolactone), referred to as pantoyl lactone or pantolactone (Fig. 4). 

Pantothenic acid is synthesized in plants and some microorganisms from pantoic acid and p-alanine. Pantoic acid is formed from 2-oxopantoic acid (4-hydroxy-3,3-dimethyl-2-oxobutyric acid) and 2-oxoisovaleric acid (3-methyl-2-oxobu-tyric acid), a precursor of valine. P-Alanine is formed by decarboxylation of l-aspartic acid. Enzymes involved include pantothenate synthetase (EC 6.3.2.1), oxopantoate reductase (EC 1.1.1.169), oxopantoate hydroxymethyltransferase (EC 4.1.2.12), and aspartate 1-decarboxylase (EC 4.1.1.12). 

The stability of pantothenic add in aqueous solutions depends greatly on the pH value. The vitamin is most stable in weakly acidic (pH 4 5) solutions, but in acidic and alkaline media the amide Hnkage is hydrolysed and pantothenic add yields pantoic add (or its salt) and fl-alanine. The enzyme pantothenase of some baderia specifically cleaves pantothenic add into the same products. In acidic solutions, pantoic acid spontaneously dehydrates to form lactone, (R)-2-hydroxy-3,3-dimethylbutano-4-lactone, which is called pantoyllactone or pantolactone (5-73). Analogously, products of panthenol hydrolysis are pantoic add... 

Mueller (257, 265) found that -alanine was a growth factor required by certain strains of C. diphtheriae, and later Mueller and Klotz (266) found that the Allen strain of C. diphtheriae responded more readily to pantothenic acid concentrates than it did to the hydrolytic products of the latter, or to an approximately equivalent quantity of 3-alanine, R. J. Williams having suggested that pantothenic acid was a compound of j9-alanine and a hydroxy acid in amide linkage. This was then demonstrated directly (404)... 

The structure of the non-nitrogenous part of pantothenic acid was re-poited as an a-hydroxy-y-lactone (247) and finally found to be a-hy-droxy-/3,j3-dimethyl-7-butyrolactone (pantoic lactone) (372, 427). Synthe-... 

Table XIV records the effects with various analogs of pantothenic acid, when the non-nitrogenous portion is varied by condensing different hydroxy acids with /3-alanine. Only very slight activity is found with any of these compounds, showing that even slight modifications of the molecular structure very greatly decrease the biological activity. The same general picture is found with higher animals for which pantothenic acid has metabolic importance.

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