Preparation and characterization of 3-monohydroxylated bile acids of different side chain length and configuration at C-3. Novel approach to the synthesis of 24-norlithocholic acid

A series of 3-monohydroxylated bile acids, in unlabeled and radioactive form, of varying side chain length and configuration at C-3 has been synthesized and rigorously characterized. They include: 3 alpha- and 3 beta-hydroxy-5 beta-androstane-17 beta-carboxylic acids (C20); 3 alpha- and 3 beta-hydroxy-5 beta-pregnan-21-oic acids (C21); 3 alpha- and 3 beta-hydroxy-23,24-bisnor-5 beta-cholan-22-oic acids (C22); 3 alpha- and 3 beta-hydroxy-24-nor-5 beta-cholan-23-oic acids (C23, norlithocholic and isonorlithocholic acids); and 3 beta-hydroxy-5 beta-cholan-24-oic acid (C24, isolithocholic acid). A novel approach to the degradation of lithocholic acid acetate to 24-norlithocholic acid is described. This degradation involves the photochemical modification of a Hunsdiecker reaction and Kornblum oxidation of the intermediate 23-bromide. The availability of these compounds makes it possible to study the metabolism and biological effects of short chain bile acids.     

Bile acids of snakes of the subfamily Viperinae and the biosynthesis of C-23-hydroxylated bile acids in liver homogenate fractions from the adder, Vipera berus (Linn.).

1. Analysis of bile salts of four snakes of the subfamily Viperinae showed that their bile acids consisted mainly of C-23-hydroxylated bile acids. 2. Incubations of 14C-labelled sodium cholate (3 alpha, 7 alpha, 12 alpha-trihydroxy-5 beta-cholan-24-oate) and deoxycholate (3 alpha, 12 alpha-dihydroxy-5 beta-cholan-24-oate) with whole and fractionated adder liver homogenates were carried out in the presence of molecular oxygen and NADPH or an NADPH-generating system. The formation of C-23-hydroxylated bile acids, namely bitocholic acid (3 alpha, 12 alpha, 23xi-trihydroxy-5 beta-cholan-24-oic acid) and 3 alpha, 7 alpha, 12 alpha, 23 xi-tetrahydroxy-cholanic acid (3 alpha, 7 alpha, 12 alpha, 23 xi-tetrahydroxy-5 beta-cholan-24-oic acid), was observed mainly in the microsomal fraction and partly in the mitochondrial fraction. 3. Biosynthetic pathways of C-23-hydroxylated bile acids are discussed.     

The effect of cholesterol feeding on gallbladder bile acids of the rabbit. Evidence that lithocholic acid is a primary bile acid in the rabbit.

The bile acid in gallbladder bile of rabbits fed a normal diet or one containing 2% (w/w) cholesterol have been determined by gas chromatography-mass spectrometry. The predominant bile acids in normally fed rabbits were 3 alpha, 7 alpha, 12 alpha-trihydroxy-5 beta-cholan-24-oic acid (cholic acid), 3 alpha, 12 alpha-dihydroxy-5 alpha-cholan-24-oic acid (allodeoxycholic acid) and 3 alpha, 12 alpha-dihydroxy-5 beta-cholan-24-oic acid (deoxycholic acid) with very much smaller amounts of 3 alpha-hydroxy-5 beta-cholan-24-oic acid (lithocholic acid) and 3 alpha, 12 beta-dihydroxy-5 beta-cholan-24-oic acid. In the cholesterol-fed animals the lithocholate became a predominant bile acid. Sulphated bile acids accounted for less than 1% of the total bile acids. It is proposed that lithocholic acid may be a primary bile acid in the cholesterol-fed rabbit, formed by an alternative pathway of biosynthesis involving hepatic mitochondria.     

Physicochemical and biological properties of natural and synthetic C-22 and C-23 hydroxylated bile acids

In order to define the effect of a side chain hydroxy group on bile acid (BA) physicochemical and biological properties, 23-hydroxylated bile acids were synthesized following a new efficient route involving the alpha-oxygenation of silylalkenes. 22-Hydroxylated bile acids were also studied. The synthesized bile acids included R and S epimers of 3 alpha,7 alpha,23-trihydroxy-5 beta-cholan-24-oic acid (23R epimer: phocaecholic acid), 3 alpha,12 alpha,23-trihydroxy-5 beta-cholan-24-oic (23R epimer: bitocholic acid), and 3 alpha,7 beta,23-trihydroxy-5 beta-cholan-24-oic acid. A 3 alpha,7 alpha,22-trihydroxy-5 beta-cholan-24-oic acid (haemulcholic acid) was also studied. The presence of a hydroxy group on the side chain slightly modified the physicochemical behavior in aqueous solution with respect to common BA: the critical micellar concentration (CMC) and the hydrophilicity were similar to naturally occurring trihydroxy BA such as cholic acid. The pKa value was lowered by 1.5 units with respect to common BA, being 3.8 for all the C-23 hydroxy BA. C-22 had a higher pKa (4.2) as a result of the increased distance of the hydroxy group from the carboxy group. When the C-23 hydroxylated BA were intravenously administered to bile fistula rats, they were efficiently recovered in bile (more than 80% unmodified) while the corresponding analogs, lacking the 23- hydroxy group, were almost completely glycine- or taurine-conjugated. On the other hand, the C-22 hydroxylated BA were extensively conjugated with taurine and less than 40% of the administered dose was secreted without being conjugated. In the presence of intestinal bacteria, they were mostly metabolized to the corresponding 7-dehydroxylated compound similar to common BA with the exception of bitocholic acid which was relatively stable. The presence of a hydroxy group at the C-23 position increased the acidity of the BA and this accounted for poor absorption within the biliary tree and efficient biliary secretion without the need for conjugation. 3 alpha,7 beta-23 R/S trihydroxy-5 beta-cholan-24-oic acids could improve the efficiency of ursodeoxycholic acid (UDCA) for gallstone dissolution or cholestatic syndrome therapy, as it is relatively hydrophilic and efficiently secreted into bile without altering the glycine and taurine hepatic pool.     

Bile salts of the green turtle Chelonia mydas (L.)

1. Bile salts of the green turtle Chelonia mydas (L.) were analysed as completely as possible. 2. They consist of taurine conjugates of 3 alpha, 7 alpha, 12 alpha, 22 xi-tetrahydroxy-5 beta-cholestan-26-oic acid (tetrahydroxysterocholanic acid) and 3 alpha 12 alpha, 22 xi-trihydroxy-5 beta-cholestan-26-oic acid, with minor amounts of 3 alpha, 7 alpha, 12 alpha-trihydroxy-5beta-cholan-24-oic acid (cholic acid), 3alpha, 12 alpha-dihydroxy-5beta-cholan-24-oic acid (deoxycholic acid) and possibly other bile acids. 3. Cholic acid and deoxycholic acid represent the first known examples of bile acids common to chelonians and other animal forms: they may indicate independent evolution in chelonians to C24 bile acids. 4. The discovery of a 7-deoxy C27 bile acid is the first evidence that C27 bile acids or their conjugates have an enterohepatic circulation.     

Identification of bile acids in the serum and urine in cholestasis. Evidence for 6alpha-hydroxylation of bile acids in man.

In this qualitative study of the pattern of bile acid excretion in cholestasis, methods are described for the isolation of bile acids from large volumes of urine and plasma. The bile acids were subjected to a group separation and identified by combined gas chromatography-mass spectrometry. The techniques were developed to allow identification of the minor components of the bile acid mixture. Four bile acids that have not previously been described in human urine and plasma were detected, namely 3beta, 7alpha-dihydroxy-5beta-cholan-24-oic acid, 3alpha, 6alpha-dihydroxy-5beta-cholan-24-oic acid (hyodeoxycholic acid), 3alpha, 6alpha, 7alpha-trihydroxy-5beta-cholan-24-oic acid (hyocholic acid) and 3alpha, 7beta, 12alpha-trihydroxy-5beta-cholan-24-oic acid. In addition three C27 steroids were found; 26-hydroxycholesterol and a trihydroxy cholestane, probably 5 beta-cholestane-3alpha, 7alpha, 26-triol were found in the sulphate fraction of plasma and urine. In the plasma sample, a sulphate conjugate of 24-hydroxycholesterol was found. The presence of these compounds probably reflects the existence of further pathways for bile acid metabolism. It is not yet known whether this is a consequence of the cholestasis or whether they are also present in normal man, at much lower concentrations.     

Identification of 3,6,7,12-tetrahydroxy-5 beta-cholan-24-oic acids in human biologic fluids

Unusual bile acids, 3 alpha, 6 alpha, 7 alpha, 12 alpha-, and 3 alpha, 6 beta, 7 beta, 12 alpha-tetrahyroxy-5 beta-cholan-24-oic acids, were identified in all amniotic fluid (four samples) and urine (six samples) from adult patients with cholestatic liver disease by gas-liquid chromatography/mass spectrometry. For the certain identification of these bile acids in the biologic samples, the chemical syntheses of 3 alpha, 6 beta, 7 alpha, 12 alpha- and 3 alpha, 6 beta, 7 beta, 12 alpha-tetrahydroxy-5 beta-cholan-24-oic acids were conducted.     

Fluorescent derivatives of bile salts. I. Synthesis and properties of NBD-amino derivatives of bile salts.

In order to visualize bile salt transport, fluorescent bile salt derivatives were synthesized by introduction of the relatively small fluorescent 4-nitrobenzo-2-oxa-1,3-diazol (NBD)-amino group in either the 3-, 7-, or 12-position of the steroid structure, thus providing a complete set of diastereomeric derivatives, 3 alpha-NBD-amino-7 alpha,12 alpha-dihydroxy-5 beta-cholan-24-oic acid, 3 beta-NBD-amino-7 alpha,12 alpha-dihydroxy-5 beta-cholan-24-oic acid, 7 alpha-NBD-amino-3 alpha,12 alpha-dihydroxy-5 beta-cholan-24-oic acid, 7 beta-NBD-amino-3 alpha,12 alpha-dihydroxy-5 beta-cholan-24-oic acid, 12 alpha-NBD-amino-3 alpha,7 alpha-dihydroxy-5 beta-cholan-24-oic acid, 12 beta-NBD-amino-3 alpha,7 alpha-dihydroxy-5 beta-cholan-24-oic acid, as well as their taurine conjugates. Their optical properties with absorption maxima at about 490 nm and emission maxima at 550 nm make them suitable for fluorescent microscopic studies. Fluorescence of the NBD-derivatives is strongly dependent on polarity of the solvent, on the concentration of the bile salt derivatives, and only slightly on temperature.     

Chemical synthesis and hepatic biotransformation of 3 alpha,7 alpha-dihydroxy-7 beta-methyl-24-nor-5 beta-cholan-23-oic acid, a 7-methyl derivative of norchenodeoxycholic acid: studies in the hamster.

A new bile acid analogue, 3 alpha,7 alpha-dihydroxy-7 beta-methyl-24-nor-5 beta-cholan-23-oic acid (7-Me-norCDCA) was synthesized from the methyl ester of norursodeoxycholic acid, and its hepatic biotransformation was defined in the hamster. To synthesize 7-Me-norCDCA, the 3 alpha-hydroxyl group of methyl norursodeoxycholate was protected as the hemisuccinate, and the 7 beta-hydroxyl group was oxidized with CrO3 to form the 7-ketone. A Grigard reaction with methyl magnesium iodide followed by alkaline hydrolysis gave 7-Me-norCDCA (greater than 70% yield). The structure of the new compound was confirmed by proton magnetic resonance and mass spectrometry. After intraduodenal administration of the 14C-labeled compound into the anesthetized biliary fistula hamster, it was rapidly and efficiently secreted into the bile; 80% of radioactivity was recovered in 2 h. After intravenous infusion, the compound was efficiently extracted by the liver and secreted into the bile (greater than 75% in 3 h). Most (93%) of the biliary radioactivity was present in biotransformation products. The major biotransformation product (48.7 +/- 6.0%) was a new compound, assigned the structure of 3 alpha,5 beta,7 alpha- trihydroxy-7 beta-methyl-24-nor-5 beta-cholan-23-oic acid (5 beta-hydroxy-7- Me-norCDCA). In addition, conjugates of 7-Me-norCDCA with taurine (13.7 +/- 5.0%), sulfate (10.3 +/- 3.0%), or glucuronide (5.1 +/- 1.7%) were formed. 7-Me-norCDCA was strongly choleretic in the hamster; during its intravenous infusion, bile flow increased 2 to 3 times above the basal level, and the calculated choleretic activity of the compound (and its metabolic products) was much greater than that of many natural bile acids, indicating that the compound induced hypercholeresis. It is concluded that the biotransformation and physiological properties of 7-Me-norCDCA closely resemble those of norCDCA. Based on previous studies, the major biological effect of the 7-methyl group in 7-Me-norCDCA is to prevent its bacterial 7-dehydroxylation in the distal intestine.     

Metabolism of bile alcohols in the perfused rabbit liver - C26 bile alcohols

The metabolism of a C26 bile alcohol (I, 24-nor-5beta-cho-lestane-3alpha, 7alpha,25-triol) was studied in the isolated perfused rabbit liver. The new bile alcohol and bile acid metabolites secreted into the bile were isolated and identified by a combination of TLC, GLC and GLC-MS. The following bile alcohols were found: II, 24-nor-5beta-cholestane-3alpha,7alpha,12alpha,25-tetrol, III, 24-nor-5beta-cholestane-3alpha,7alpha,12alpha,25,26-pentol; IV, 24-nor-5beta-cholest-23-ene-3alpha,7alpha,12alpha-triol; and V, 24-nor-5beta-cholest-23-ene-3alpha,7alpha-diol. In the bile acid fraction, 24-nor-cholic acid and 3alpha,7alpha,12alpha-trihydroxy-24-nor-5beta-cholest-23-en-26-oic acid were present. The perfused nor-triol was not resistant to 12alpha-hydroxylation.     

Synthesis of 3 alpha,6 beta,7 alpha,12 beta- and 3 alpha,6 beta,7 beta,12 beta-tetrahydroxy-5 beta-cholanoic acids.

Chemical synthesis of 3 alpha,6 beta,7 alpha,12 beta- and 3 alpha,6 beta,7 beta,12 beta-tetrahydroxy-5 beta-cholan-24-oic acids is described. 3 alpha,12 beta-Dihydroxy-5 beta-chol-6-en-24-oic acid used as the starting material in the synthesis was prepared via oxidation of 3 alpha,12 alpha-dihydroxy-5 beta-chol-6-en-24-oic acid 3-hemisuccinate at C-12 followed by reduction with potassium/tertiary amyl alcohol. alpha-Epoxidation of the ester diacetate of 3 alpha,12 beta-dihydroxy-5 beta-chol-6-en-24-oic acid with m-chloroperbenzoic acid followed by cleavage of the epoxide with acetic acid and alkaline hydrolysis yielded 3 alpha,6 beta,7 alpha,12 beta-tetrahydroxy-5 beta-cholan-24-oic acid (overall yield 25%). N-Methylmorpholine-N-oxide-catalyzed osmium tetroxide oxidation of the ester diacetate of 3 alpha,12 beta-dihydroxy-5 beta-chol-6-en-24-oic acid followed by alkaline hydrolysis yielded 3 alpha,6 beta,7 beta,12 beta-tetrahydroxy-5 beta-cholan-24-oic acid (overall yield 33%). The structures of the synthesized bile acids were confirmed from their proto nuclear magnetic resonance and mass spectral fragmentation patterns.     

Synthesis of potential cholelitholytic agents: 3 alpha,7 alpha,12 alpha-trihydroxy-7 beta-methyl-5 beta-cholanoic acid, 3 alpha,7 beta,12 alpha-trihydroxy-7 alpha-methyl-5 beta-cholanoic acid, and 3 alpha,12 alpha-dihydroxy-7 xi-methyl-5 beta-cholanoic acid

This report describes the chemical synthesis of six new bile acid analogs, namely, 3 alpha,7 alpha,12 alpha-trihydroxy-7 beta-methyl-5 beta-cholanoic acid (7 beta-methyl-cholic acid), 3 alpha,7 beta,12 alpha-trihydroxy-7 alpha-methyl-5 beta-cholanoic acid (7 alpha-methyl-ursocholic acid), 3 alpha,12 alpha-dihydroxy-7 xi-methyl-5 beta-cholanoic acid (7 xi-methyl-deoxycholic acid), 3 alpha,12 alpha-dihydroxy-7-methyl-5 beta-chol-7-en-24-oic acid, 3 alpha,12 alpha-dihydroxy-7-methyl-5 beta-chol-6-en-24-oic acid, and 3 alpha,12 alpha-dihydroxy-7-methylene-5 beta-cholan-24-oic acid. The carboxyl group of the starting material 3 alpha,12 alpha-dihydroxy-7-oxo-5 beta-cholanoic acid was protected by conversion to its oxazoline derivative. A Grignard reaction of the bile acid oxazoline with CH3MgI followed by acid hydrolysis gave two epimeric trihydroxy-7-methyl-cholanoic acids and three dehydration products. The latter were purified by silica gel column chromatography and silica gel-AgNO3 column chromatography of their methyl ester derivatives. Catalytic hydrogenation of 3 alpha,12 alpha-dihydroxy-7-methyl-5 beta-chol-6-en-24-oic acid and 3 alpha,12 alpha-dihydroxy-7-methylene-5 beta-cholan-24-oic acid gave 3 alpha,12 alpha-dihydroxy-7 xi-methyl-5 beta-cholanoic acid. The configuration of the 7-methyl groups and the position of the double bonds were assigned by proton nuclear magnetic resonance spectroscopy and the chromatographic and mass spectrometric properties of the new compounds. These compounds were synthesized for the purpose of exploring new and potentially more effective cholelitholytic agents. The hydrophilic bile acids 7 beta-methyl-cholic acid and 7 alpha-methyl-ursocholic acid are of particular interest because they should be resistant to bacterial 7-dehydroxylation.     

Effect of bile acid analogs on 7 alpha-dehydroxylase activity in Eubacterium sp. V.P.I. 12708

7 beta-Methyl-chenodeoxycholic acid (7-MeCDC, 3 alpha, 7 alpha-dihydroxy-7 beta-methyl-5 beta-cholan-24-oic acid), 7 alpha-methyl-ursodeoxycholic acid (7-MeUDC, 3 alpha, 7 beta-dihydroxy-7 alpha-methyl-5 beta-cholan-24-oic acid), 7 xi-methyl-lithocholic acid (7-MeLC, 3 alpha-hydroxy-7 xi-methyl-5 beta-cholan-24-oic acid) and ursodeoxycholylsarcosine (UDCS) were tested as inhibitors of bacterial bile acid 7 alpha-dehydroxylase activity. At a concentration of 50 microM, 7-MeCDC and 7-MeUDC inhibited enzyme activity by 66% and 12%, respectively. 7 alpha-Dehydroxylase activity was not inhibited in the presence of 7-MeLC and UDCS. None of the four bile acid analogs tested inhibited the growth of Eubacterium sp. V.P.I. 12708 at concentrations up to 100 microM.     

Absolute configuration at C-24 of 5 beta-ranol, a principal bile alcohol of the bullfrog

The stereochemistry of the hydroxyl group at C-24 in 5 beta-ranol (27-nor-5 beta-cholestane-3 alpha,7 alpha,12 alpha,24,26-pentol) a principal bile alcohol of the bullfrog which is structurally related to the major human urinary bile alcohol, 27-nor-5 beta-cholestane-3 alpha,7 alpha,12 alpha,24,25-pentol, is described. Two isomers (IIIa and IIIb) at C-24 of 27-nor-5 beta-cholest-25-ene-3 alpha,7 alpha,12 alpha, 24-tetrol were synthesized from cholic acid (I) by the conversion to 3 alpha, 7 alpha, 12 alpha-triacetoxy-5 beta-cholan-24-al (II) followed by a Grignard reaction with vinylmagnesium bromide. The absolute configurations at C-24 of the unsaturated tetrols (IIIa and IIIb) were elucidated as S and R, respectively, by means of the difference of the reactivity to Sharpless oxidation, a stereoselective epoxidation. Catalytic hydrogenation of each delta 25-tetrol (IIIa or IIIb) gave (24R)- or (24S)-27-nor-5 beta-cholestane-3 alpha,7 alpha,12 alpha, 24-tetrol (IVa or IVb). The configurations at C-24 of two isomeric 3 alpha,7 alpha,12 alpha,24-tetrahydroxy-27-nor-5 beta-cholestan-26-oic acids (Va and Vb) were determined as S and R, respectively, by means of their conversion into the saturated tetrols (IVa and IVb) of known absolute configurations by a Kolbe electrolytic coupling with acetic acid. The lithium aluminum hydride reduction product of the 24R-acid (Vb) was identical with the naturally occurring 5 beta-ranol, hence 5 beta-ranol has the 24R configuration.     

Identification of a novel bile acid in swans, tree ducks, and geese: 3alpha,7alpha,15alpha-trihydroxy-5beta-cholan-24-oic acid

By HPLC, a taurine-conjugated bile acid with a retention time different from that of taurocholate was found to be present in the bile of the black-necked swan, Cygnus melanocoryphus. The bile acid was isolated and its structure, established by (1)H and (13)C NMR and mass spectrometry, was that of the taurine N-acyl amidate of 3alpha,7alpha,15alpha-trihydroxy-5beta-cholan-24-oic acid. The compound was shown to have chromatographic and spectroscopic properties that were identical to those of the taurine conjugate of authentic 3alpha,7alpha,15alpha-trihydroxy-5beta-cholan-24-oic acid, previously synthesized by us from ursodeoxycholic acid. By HPLC, the taurine conjugate of 3alpha,7alpha,15alpha-trihydroxy-5beta-cholan-24-oic acid was found to be present in 6 of 6 species in the subfamily Dendrocygninae (tree ducks) and in 10 of 13 species in the subfamily Anserinae (swans and geese) but not in other subfamilies in the Anatidae family. It was also not present in species from the other two families of the order Anseriformes. 3alpha,7alpha,15alpha-Trihydroxy-5beta-cholan-24-oic acid is a new primary bile acid that is present in the biliary bile acids of swans, tree ducks, and geese and may be termed 15alpha-hydroxy-chenodeoxycholic acid.     

Appearance of atypical 3 alpha,6 beta,7 beta,12 alpha-tetrahydroxy-5 beta-cholan-24-oic acid in spgp knockout mice

Bile formation and its canalicular secretion are essential functions of the mammalian liver. The sister-of-p-glycoprotein (spgp) gene was shown to encode the canalicular bile salt export protein, and mutations in spgp gene were identified as the cause of progressive familial intrahepatic cholestasis type 2. However, target inactivation of spgp gene in mice results in nonprogressive but persistent cholestasis and causes the secretion of unexpectedly large amounts of unknown tetrahydroxylated bile acid in the bile. The present study confirms the identity of this tetrahydroxylated bile acid as 3 alpha,6 beta,7 beta,12 alpha-tetrahydroxy-5 beta-cholan-24-oic acid. The data further show that in serum, liver, and urine of the spgp knockout mice, there is a significant increase in the concentration of total bile salts containing a large amount of tetrahydroxy-5 beta-cholan-24-oic acid. The increase in total bile acids was associated with up-regulation of the mRNA of cholesterol 7 alpha-hydroxylase in male mice only. It is suggested that the lower severity of the cholestasis in the spgp knockout mice may be due to the synthesis of 3 alpha,6 beta,7 beta,12 alpha-tetrahydroxy-5 beta-cholan-24-oic acid, which neutralizes in part the toxic effect of bile acids accumulated in the liver.     

Bile salts of the coelacanth, Latimeria chalumnae

Bile salts of the coelacanth, Latimeria chalumnae, Smith, have been analyzed and shown to have three bile alcohols, latimerol, 5 alpha-cyprinol, and 5 alpha-cholestane-3 beta, 7 alpha,-12 alpha,25,26-pentol, two C24 bile acids, chenodeoxycholic acid and cholic acid, one C26 bile acid, probably 3 beta, 7 alpha, 12 alpha-trihydroxy-27-nor-5 alpha-cholestan-26-oic acid, and two C27 bile acids, 3 alpha,7 alpha,12 alpha-trihydroxy-5 alpha-cholestan-26-oic acid and 3 beta,7 alpha,12 alpha-trihydroxy-5 alpha-cholestan-26-oic acid as determined by gas-liquid chromatography and gas-liquid chromatography-mass spectrometry.     

Anodic electrochemical oxidation of cholic acid

Regioselectivity in the anodic electrochemical oxidation of cholic acid with different anodes is described. The oxidation with PbO(2) anode affords the dehydrocholic acid in quantitative yield after 22 h. 3alpha,12alpha-Dihydroxy-7-oxo-5beta-cholan-24-oic acid (59%) and 3alpha-hydroxy-7,12-dioxo-5beta-cholan-24-oic acid (51%) are obtained stopping the reaction at lower time. The rate of the OH-oxidation is C7 > C12 > C3. The electro-oxidation with platinum foil anode gives selectively the 7-ketocholic acid in 40% yield. On the other hand, the graphite plate anode, varying the reaction conditions, produces selectively the dehydrocholic acid in quantitative yield or the 3alpha,12alpha-dihydroxy-7-oxo-5beta-cholan-24-oic acid (96%) while the 3alpha,7alpha-dihydroxy-12-oxo-5beta-cholan-24-oic acid (34%) is obtained together with the other oxo acids.     

Classical bile acids in animals, beta-phocaecholic acid in ducks

1. Bile samples of different animals were analysed and the percentage content of classical bile acids was determined. 2. Herbivorous birds mostly excreted a large proportion of chenodeoxycholic acid. 3. The anteater (Myrmecophaga tridactyla) excreted deoxycholic acid most probably as a primary bile acid. 4. In the bile of ducks (Anas platyrhynchos) a large amount of (23R)3 alpha, 7 alpha, 23-trihydroxy-5 beta-cholan-24-oic acid (beta-phocaecholic acid) was found.     

Comparative studies of bile salts. A new type of bile salt from Arapaima gigas (Cuvier) (family Osteoglossidae)

1. Arapaima gigas bile salts were hydrolysed by alkali or cleaved with dioxan-trichloroacetic acid to give cholic acid, arapaimic acid, arapaimol-A and arapaimol-B. 2. I.r., n.m.r. and mass spectroscopy and [alpha](D) measurements indicated that arapaimic acid and arapaimol-A and -B are respectively 2alpha,3alpha,7alpha,12alpha-tetrahydroxy-5beta,25in-cholestan-26-oic acid, 5beta,25R-cholestane-2beta,3alpha,7alpha,12alpha,26-pentol and 5beta-cholestane-2beta,3alpha,7alpha,12alpha,26,27-hexol. 3. Partial synthesis of 2beta,3alpha,7alpha,12alpha-tetrahydroxy-5alpha- and -5beta-cholan-24-oic acid and their spectral examination fully confirmed these conclusions. 4. A. gigas bile salts show primitive features in that they comprise alcohol sulphates and a C(27) acid; they are also specialized in showing 2beta-hydroxylation.