Synthesis of methyl 2,4-di-O-methyl-3-O-(2-O-methyl-alpha-L-rhamnopyranosyl)-alpha-L- rhamnopyranoside and methyl 2,4-di-O-methyl-3-O-[2-O-methyl-3-O-(2-O-methyl-alpha-L-fucopyranosyl)- alpha-L-rhamnopyranosyl]-alpha-L-rhamnopyranoside: di- and tri-saccharide segments of a phenolic glycolipid of Mycobacterium kansasii.

Syntheses of the title glycosides are described. The critical O-glycosylations were carried out in the presence of boron trifluoride etherate with a high degree of alpha-selectivity.     

Preparative synthesis of C-(alpha-D-glucopyranosyl)-alkenes and -alkadienes: Diels-Alder reaction

The reaction of 2,3,4,6-tetra-O-benzyl-1-O-(p-nitrobenzoyl)-alpha-D-glucopyranose with (E)-penta-2,4-dienyltrimethylsilane and boron trifluoride etherate in acetonitrile afforded stereoselectively (E)-5-(tetra-O-benzyl-alpha-D-glucopyranosyl)-1,3-pentadiene in good yield. The readily available penta-O-benzoyl-alpha-D-glucopyranose reacted with allyltrimethylsilane in the presence of boron trifluoride etherate in acetonitrile to give 3-(tetra-O-benzoyl-alpha-D-glucopyranosyl)-1-propene and its beta anomer in yields of 60% and 2.3%, respectively. Diels-Alder cycloaddition of maleic anhydride to diene 1 afforded the adduct cis,cis-3-(tetra-O-benzyl-alpha-D-glucopyranosylmethyl)cyclohex -4-ene- 1,2-dicarboxylic anhydride in high yield.     

Acid-catalysed Reactions of Methyl β-(3,4-Dimethoxyphenyl) glycidate

Methyl trans-β-(3,4-dimethoxyphenyl)glycidate was found to rearrange to methyl 3,4-dimethoxyphenylpyruvate in high yield in DMSO, DMF or HMPT solution in the presence of boron trifluoride etherate or sulfuric acid at room temperature. It was also revealed that the glycidate, when treated with boron trifluoride in methanol at room temperature, opened at the β-position to give methyl β-(3,4-dimethoxyphenyl)-α-hydroxy-β-methoxy-propionate in 94% yield, which was a mixture of erythro and threo isomers in the ratio of 1 to 2.     

Syntheses and preliminary biological studies of four meso-Tetra[(nido-carboranylmethyl)phenyl]porphyrins

Two meso-tetra[(nido-carboranylmethyl)phenyl]porphyrins (para- and meta-regioisomers) and their corresponding Zn(II) complexes have been synthesized with the aim of studying the effect of carborane distribution and metalation on the biological properties of this series of compounds. In vitro cell toxicity, uptake/efflux, and subcellular localization using rat 9L, mouse B16 and/or human U-373MG cells were evaluated. All four amphiphilic porphyrins display very low cytotoxicities and time- and concentration-dependent uptake by cells, which is influenced by serum proteins. Preliminary subcellular localization studies suggest that one of these compounds localizes in close proximity to the cell nucleus. All four nido-carboranylporphyrins show promise as boron-carriers for the boron neutron capture therapy of cancers, particularly the metal-free nido-carboranylporphyrins 5 and 12, which are able to deliver higher amount of boron to cells in vitro than the corresponding zinc complexes.     

Synthesis of 4-cyano and 4-nitrophenyl 1,6-dithio-D-manno-, L-ido- and D-glucoseptanosides possessing antithrombotic activity

1,6-Anhydro-3,4-O-isopropylidene-1-thio-D-mannitol was converted into its sulfoxide which after hydrolysis, acetylation and subsequent Pummerer rearrangement gave the penta-O-acetyl-1-thio-D-mannoseptanose anomers in excellent yield. This anomeric mixture was used as donor for the glycosylation of 4-nitro- and 4-cyanobenzenethiol in the presence of boron trifluoride etherate and trimethylsilyl triflate, respectively, to yield the corresponding thioseptanosides in high yield. The same strategy was applied for the synthesis of the corresponding L-idothioseptanosides using 1,6-anhydro-3,4-O-isopropylidene-1-thio-L-iditol as starting material. The penta-O-acetyl-D-glucothioseptanose donors could not be synthesised the same way, as the Pummerer reaction of the corresponding tetra-O-acetyl-1,6-thioanhydro-1-thio-D-glucitol sulfoxides led to an inseparable mixture of the corresponding L-gulo- and D-glucothioseptanose anomers. Therefore, D-glucose diethyl dithioacetal was converted via its 2,3,4,5-tetra-O-acetyl-6-S-acetyl derivative into an anomeric mixture of its 6-thio-septanose and -furanose peracetates which could be separated by column chromatography. Condensation of the 6-thio-glucoseptanose peracetates with 4-cyano- and 4-nitrobenezenethiol in the presence of boron trifluoride etherate afforded anomeric mixtures of the corresponding thioseptanosides. The D-manno-, L-ido- and D-glucothioseptanosides obtained after Zemplén deacetylation of these mixtures were tested for their oral antithrombotic activity.     

On methylation of unsaturated acids using boron trihalide-methanol reagents

Methanolysis of unsaturated fatty acids and triglycerides was carried out with boron trihalide-methanol reagents of various ages. Boron trichloride-methanol produced esters apparently free from contaminants; boron trifluoride caused some loss of highly unsaturated esters after 90 min at 100 or 120 degrees C in Teflon-lined screw-cap vials and at 120 degrees C in ampoules. The losses were more marked when the reactions were carried out in vinyl-lined screw-cap vials. Noticeable losses did not occur with any of the vessel types when BCl(3)-CH(3)OH was the methylating agent. Long-term studies at 80 degrees C further demonstrated that BCl(3)-CH(3)OH caused less loss of unsaturated acid than did BF(3)-CH(3)OH.     

Novel glycosylation of the nitroxyl radicals with peracetylated glycosyl fluorides using a combination of BF(3) x OEt(2) and an amine base as promoters

Glycosylation of the nitroxyl radicals, 4-acetoxy-2,2,6,6-tetramethylpiperidin-1-oxyl (4-acetoxy-TEMPO) and 3-carbamoyl-2,2,5,5-tetramethylpyrollin-1-oxyl (3-carbamoyl-PROXYL) with peracetylglycosyl fluoride as the glycosyl donor, in the presence of boron trifluoride diethyl etherate (BF(3) x OEt(2)) and an amine base afforded the corresponding hydroxylamine-O-glycosides in 25-100% yields.     

Synthesis of 7-oxabicyclo[2.2.1]hept-5-en-2-yl derivatives and their screening for antimicrobial and antioxidant properties

Novel 7-oxabicyclo[2.2.1]hept-5-en-2-yl derivatives have been synthesized using boron trifluoride diethyl etherate catalyzed Diels–Alder reaction. This method presents considerable synthetic advantages in terms of high atom economy, mild reaction condition and good yields. The synthesized compounds have been screened for their antibacterial and antioxidant activities.     

The chemical and enzymatic oxidation of hematohemin IX. Identification of hematobiliverdin IX alpha as the sole product of the enzymatic oxidation

Oxidative cleavage of hematohemin IX in pyridine solution in the presence of ascorbic acid (coupled oxidation), followed by esterification of the products with boron trifluoride/methanol produced the four possible hematobiliverdin dimethyl esters in 11.1% overall yield. Transetherifications took place simultaneously with the esterification reaction and resulted in the formation of the dimethyl ester of hematobiliverdin IX gamma 8a,13a-dimethyl ether (1.8%), the dimethyl ester of hematobiliverdin IX beta 13a,18a-dimethyl ether (1.9%), the dimethyl ester of hematobiliverdin IX delta 8a-monomethyl ether (1.4%), and the dimethyl ester of hematobiliverdin IX alpha 18a-monomethyl ether (0.4%). The latter was the sole product obtained after the enzymatic oxidation of hematohemin with heme oxygenase, after esterification of the reaction product with boron trifluoride/methanol. When the esterification step was omitted hematobiliverdin IX alpha was obtained from the enzymatic oxidation. The structures of the hematobiliverdin derivatives were secured by their NMR and mass spectra data. Saponification of the dimethyl esters afforded the hematobiliverdin methyl ethers, which were excellent substrates of biliverdin reductase and were readily reduced to the corresponding bilirubins. Hematobiliverdin IX alpha was also a good substrate of biliverdin reductase. It is concluded that the enzymatic oxidation of hematohemin IX by heme oxygenase is alpha-selective, while biliverdin reductase shows no selectivity in the reduction of the four hematobiliverdin isomers.     

Determination of porphyrins and biliverdin in bile and excreta of birds by a single liquid chromatography-ultraviolet detection analysis

Methods developed for porphyrin analysis have low recoveries and/or poor precision for the less polar protoporphyrin IX. We describe a simple method of analysis of porphyrins and biliverdin in bile and excreta of birds based on extraction with HCl 3N: acetonitrile and HPLC/UV analyses. Recoveries were good for protoporphyrin IX and other porphyrins (>79%). Applications of this method showed that porphyrins and biliverdin in birds excreta are mainly of biliary-fecal origin rather than urinary origin. Biliverdin and protoporphyrin IX increased proportionately more than the rest of the porphyrins and coproporphyrin III increased more than coproporphyrin I in the bile of Pb-poisoned mallards.     

Chromatography of water-soluble porphyrins and their conjugates with proteins

The chromatographic behaviour of tetra- and octacarboxylic porphyrins and tetra-(p-sulphophenyl)-porphin was being studied by HPLC using Protein Pak and TSK-type gel permeation columns. The mobility of the porphyrins on the carriers depended on the ionic strength of the eluating buffer Tris-HCl. The conditions for separation of the porphyrins and their protein conjugates were optimized. The separation was performed under mild conditions with minimum denaturation of conjugates. The purification technique can be used to separate porphyrin conjugates with various proteins. The technique can be also used in conventional column chromatography on Toyopearl supports.     

Synthesis and anti-inflammatory activity of N-phthalimidomethyl 2,3-dideoxy- and 2,3-unsaturated glycosides

3,4,6-Tri-O-acetyl-D-galactal, 3,4,6-tri-O-acetyl-D-glucal and 3,6,2',3',4'6'-hexa-O-acetyl-D-lactal were reacted with N-hydroxymethylphthalimide and boron trifluoride etherate to produce the corresponding phthalimidomethyl unsaturated glycosides via Ferrier rearrangement. When the galactal derivative was used, a non-Ferrier rearrangement product was also isolated as a minor product under classical Ferrier conditions. Phthalimidomethyl deoxy glycosides were readily prepared by hydrogenation of the unsaturated glycosides. Following deacetylation, the anti-inflammatory activities of these compounds were tested on mice and three were found to possess potent activity compared to hydrocortisone sodium succinate (HSS).     

The cyanation reaction of O-acetylated S-glycosyl phosphorothioates

The reaction of alpha- and beta-1-S-phosphorothioates of per-O-acetylated monosaccharides (galactose, xylose, glucose) with trimethylsilyl cyanide in the presence of boron trifluoride etherate has been investigated. It has been established that in dichloromethane 1,2-O-cyanoethylidene derivatives of aldoses are formed in high yields. When the reaction was carried out in acetonitrile, peracetylated galactosyl cyanide was formed as the major product.     

Positive cooperativity in the cellular uptake of a boronated porphyrin

This work was undertaken to assess the kinetics of boronated porphyrin cellular uptake, which has been reported to occur by way of the low-density lipoprotein receptors. Because of current interest in the use of boronated porphyrins in boron neutron capture therapy of tumors, this pathway was investigated for the cellular uptake of a boronated porphyrin (tetrakis-carborane-carboxylate, esters of 2,4-bis (alpha,beta-dihydroxyethyl) deuteroporphyrin IX). Boron uptake occurred even without low-density lipoprotein in the culture medium. Pre-incubation of V-79 Chinese hamster cells for 24 h in medium containing delipidized fetal bovine serum markedly increased the subsequent uptake of boron when compared with cells pre-incubated with medium containing 10% fetal bovine serum. The increased uptake was characterized by greater affinity for boronated porphyrin, compared to cells pre-incubated in 10% fetal bovine serum. Twenty-four hour preincubation of cells with increasing concentrations of LDL added to delipidized medium suppressed the up-regulation of the boron level. In contrast, incubation with added acetylated LDL did not prevent the up-regulation of boron uptake. Positive cooperativity was demonstrated by Hill and Scatchard plots. It is concluded that uptake of boronated porphyrin is characterized by positive cooperativity, that its uptake is markedly enhanced when preincubated in delipidized serum, and that significant uptake occurs even in the absence of low density lipoprotein in the medium. These data suggest a novel way for enhancing uptake of boron (and perhaps other agents) into tissues using carrier porphyrins, by increasing the number and/or affinity of cellular LDL receptors.     

Analytik Atypischer Fettsäuren in biologischen Matrizes

By combined application of chemical pretreatments, capillary gas-chromatography and mass spectrometry it was possible to enlighten the structure of atypical fatty acids with hydroxy groups and cyclopropane rings under the use of only a few of reference substances. The direct alkaline saponification of the sample with liberation of fatty acids and following methylation with boron trifluoride/methanol or diazomethane was proved to be the best method regarding to precision and speed of the sample cleanup.     

Porphyrin-mediated boron neutron capture therapy: a preclinical evaluation of the response of the oral mucosa

Preclinical studies are in progress to determine the potential of boron neutron capture therapy (BNCT) for the treatment of carcinomas of the head and neck. Recently, it has been demonstrated that various boronated porphyrins can target a variety of tumor types. Of the porphyrins evaluated so far, copper tetracarboranylphenyl porphyrin (CuTCPH) is potentially a strong candidate for clinical use. In the present investigation, the response of the oral mucosa to CuTCPH-mediated boron neutron capture (BNC) irradiation was assessed using the ventral surface of the tongue of adult male Fischer 344 rats, a standard rodent model. CuTCPH was administered by intravenous infusion, at a dose of 200 mg/kg body weight, over a 48-h period. Three days after the end of the administration of CuTCPH, biodistribution studies indicated very low levels of boron (<2 microg/g) in the blood. Levels of boron in tongue tissue were 39.0 +/- 3.8 microg/g at this time. This was the time selected for irradiation with single doses of thermal neutrons from the Brookhaven Medical Research Reactor. The estimated level of boron-10 in the oral mucosa was used in the calculation of the physical radiation doses from the 10B(n,alpha)7Li reaction. This differs from the approach using the present generation of clinical boron carriers, where boron levels in blood at the time of irradiation are used for this calculation. Dose-response curves for the incidence of mucosal ulceration were fitted using probit analysis, and the doses required to produce a 50% incidence of the effect (ED50 +/- SE) were calculated. Analysis of the dose-effect data for CuTCPH-mediated BNC irradiation, compared with those for X rays and thermal neutrons alone, gave a compound biological effectiveness (CBE) factor of approximately 0.04. This very low CBE factor would suggest that there was relatively low accumulation of boron in the key target epithelial stem cells of the oral mucosa. As a consequence, with low levels of boron (<2 microg/g) in the blood, the response of the oral mucosa to CuTCPH-mediated BNCT will be governed primarily by the radiation effects of the thermal neutron beam and not from the boron neutron capture reaction [10B(n,alpha)7Li].     

Total syntheses of three copper (II) tetracarboranylphenylporphyrins containing 40 or 80 boron atoms and their biological properties in EMT-6 tumor-bearing mice

Three carboranyltetraphenylporphyrins containing 40 or 80 boron atoms were synthesized and evaluated for their biodistribution and toxicity in EMT-6 tumor-bearing mice. Copper (II) meso-5,10,15,20-tetrakis[3-methoxy-4-(o-carboranylmethoxy)phenyl]porphyrin, 6, and copper (II) meso-5,10,15,20-tetrakis[3-hydroxy-4-(o-carboranylmethoxy)phenyl]porphyrin, 8, are B40 congeners with different lipophilicities, each less than their B80 congener, copper (II) meso-5,10,15,20-tetrakis[m-(3,5-di-o-carboranylmethoxybenzyloxy)phenyl]porphyrin, 18. Two days after the last of a series of i.p. injections in BALB/c mice bearing EMT-6 mammary tumors, a dose of 185 mg/kg 6 (54 mg/kg B) delivered over 3.5 times the concentration of boron to tumor (169 microg/g B) than did 118 mg/kg 8 (36 mg/kg B), which delivered 35 microg/g B, or 87 mg/kg 18 (30 mg/kg B), which delivered 46 microg/g B. The tumor-to-blood and tumor-to-brain boron concentration ratios at that time for all three porphyrins exceeded 80:1. Two days after the last injection, there resulted moderate thrombocytopenia that essentially disappeared two days later from 6 and 18, and mild leukocytosis from 6, 8, and 18, all of which were clinically inconsequential. Thus, 6 may rank among the most clinically promising carboranyl porphyrins ever made to deliver 10B to tumors for boron neutron-capture therapy (BNCT) that has also been tested for its toxicity in vivo.     

Novobiocin-related compounds: synthesis of 3-benzoylamino-2-oxo-2H-1-benzopyran-7-yl D-glycopyranosides by the trichloroacetimidate methodology

A general stereoselective method for the synthesis of 4-deoxynovobiocin-related glycosides is described. 3-Benzoylamino-2H-1-benzopyran-7-yl 2,3,4,6-tetra-O-acetyl-D-glycopyranosides of glucose, galactose and mannose were synthesised from appropriate O-glycosyltrichloroacetimidates and N-(7-hydroxy-2-oxo-2H-1-benzopyran-3-yl)benzamides in boiling methylene chloride in the presence of boron trifluoride etherate. Heating of these products in a mixture of triethylamine and methanol gave the corresponding deprotected 3-benzoylamino-2-oxo-2H-1-benzopyran-7-yl beta-D-glycopyranosides.     

A new method for the detritylation of 1,2-diradyl-3-O-tritylglycerols

The 3-O-trityl derivatives of 1,2-diacylglycerols, 1-O-alkyl-2-acylglycerols and 1,2-di-O-alkylglycerols alkyglycerols are detritylated with boron trifluoride—methanol in methylene chloride. The reaction is complete within 30 min at 0°C. Acyl migration does not occur.     

Potential bile acid metabolites. 14. Hyocholic and muricholic acid stereoisomers

The complete set of the eight theoretically possible stereoisomeric 3,6,7-trihydroxy-5 beta-cholanic acids, four of which are new, related to hyocholic and muricholic acids were prepared from chenodeoxycholic acid. The principal reactions used were 1) cis-dihydroxylation of delta 6-compounds with osmium tetroxide/N-methylmorpholine N-oxide; 2) trans-dihydroxylation of 6 alpha, 7 alpha-epoxy compounds with boron trifluoride etherate in N,N-dimethyl-formamide; 3) inversion of equatorial 3 alpha-hydroxylated compounds to the corresponding 3 beta-epimers with diethyl azodicarboxylate/triphenylphosphine/formic acid; and 4) stereoselective reduction of 7-keto derivatives with zinc borohydride (or sodium borohydride) and by metallic potassium/tert-amyl alcohol.