Acetal Formation is Responsible for the Non-Closed Form of Monensin A in Methanolic Solution

NMR evidence shows that so-called non-closed form of monensin A free acid reported to exist in methanol is in fact due to acetal formation at C-25. The 25-alkoxy derivatives retain this conformation even in non-polar media.

Crystal Structures of Cyclosporin Derivatives: O-Acetyl-(4R)-4-(E-2-butyl)-4,N-dimethyl-L-threonyl-cyclosporin A and O-Acetyl-(4R)-4-[E-2-(4-bromobutyl)]-4,N-dimethyl-L-threonyl-cyclosporin A

The structures of O-acetyl-(4R)-4-(E-2-butyl)-4,N-dimethyl-L-threonyl-cyclosporin A (1) and O-acetyl-(4R)-4-[E-2-(4-bromobutyl)]-4,N-dimethyl-L-threonyl-cyclosporin A (2) were determined by X-ray diffraction methods and compared with the structure of related cyclosporins. In contrast to expectation, neither the acetylation nor the subsequent bromination of 1 affects the conformation and packing of cyclosporins in the solid state. Both compounds are isomorphous and crystallize in the orthorhombic space group P212121 with a = 12.936(2) Å, b = 15.590(2) Å, c = 36.280(3) Å, and a = 12.916(3) Å, b = 15.675(4) Å, c = 36.715(7) Å, for 1 and 2, respectively.

A Hetero Diels-Alder Access to (Z)-Zeatin and (Z)-Isozeatin

(Z)-6-(4-Hydroxy-3-methylbut-2-en-1-ylamino)purine, (Z)-zeatin, and the isomeric (Z)-isozeatin, both free from the E isomers, were prepared using the cycloaddition of the in situ generated tert-butyl nitrosoformate on isoprene. A mixture of tert-butyl 5(and 4)-methyl-3,6-dihydro-2H-1,2-oxazine-2-carboxylates thus formed was deprotected and reductively cleaved to (Z)-4-amino-2(and 3)-methylbut-2-en-1-ols, which were chromatographically separated and finally alkylated with 6-chloropurine to give the title compounds.

Pyridoxine as a Substrate for Screening Synthetic Potential of Glycosidases

The reactions of glycosidases with pyridoxine were used for testing their ability to make new glycosidic bonds. Of 35 glycosidases examined, some exhibited regiospecificity towards one primary alcoholic group; glycosylation of phenolic hydroxyl group was not observed. A series of new glycosides of pyridoxine, 2-acetamido-2-deoxy-β-D-glucopyranosides, α-D-manno- pyranosides, and one α-D-galactopyranoside were prepared and completely characterized by MS and NMR.

Destruxin Ed1 a cyclopeptide from the fungus Metarhizium anisopliae

A new destruxin Ed1 has been isolated from the entomopathogenic fungus Metarhizium anisopliae. Its structure was deduced from the NMR and mass spectral data.

Rapid screening of destruxins by liquid chromatography/mass spectrometry

A liquid chromatographic/mass spectrometric (LC/MS) method utilizing an atmospheric pressure chemical ionization (APCI) interface and in-source collisionally induced dissociation (CID) was developed for the rapid screening of the cyclic hexadepsipeptides destruxins, produced by the fungi Metarhizium anisopliae and Trichothecium roseum. The APCI mass spectra are fully consistent with the high-energy CID data but the sequence ions are abundant over the whole mass range. In addition to 22 known destruxins, two new representatives of this family were detected by LC/MS analysis: destruxin Ed1 and roseotoxin A were isolated and their structures were inferred from MS/MS and NMR data.

Molecular Structure of cis- and trans-Tergurides

Four isomers of terguride, a semisynthetic ergot alkaloid derivative, have been prepared by catalytic hydrogenation of (5R,8S)- and (5S,8S)-lisuride [1,1-diethyl-3-(6-methyl-8-ergolenyl)urea]. Relative stereochemistry of the isomers is based on NMR and CD spectra. Absolute configuration of all the series has been confirmed by the X-ray crystal structure determination of (5R,8S,10S)-terguride 2-bromobenzoate [1,1-diethyl-3-(6-methyl-8-isoergolenyl)urea, cis-dihydrolisuride].

beta-Glucosylation of chitooligomers by galactosyltransferase

Galactosyltransferase from bovine milk was found to be able to utilise UDP-Glc to transfer Glc onto GlcNAc and chitooligomers[-beta-GlcNAc-(1-->4)-]n, n = 2-4. beta-Glucosylated products were used in binding studies with NKR-P1A protein cloned from rat natural killer cells.

Biotransformation of diethenylbenzenes, V. Identification of urinary metabolites of 1,2-diethenylbenzene in the rat

1. Biotransformation of 1,2-diethenylbenzene (1) in rat was studied. Five urinary metabolites were isolated by extraction of acid hydrolysed urine and identified by nmr and mass spectroscopy, namely, 1-(2-ethenylphenyl)ethane-1,2-diol (2) 2-ethenylmandelic acid (3), 2-ethenylphenylglyoxylic acid (4), 2-ethenylphenylacetylglycine (5) N-acetyl-S-[1-(2-ethenylphenyl)-2-hydroxyethyl]cysteine (6) and N-acetyl-S-[2-(2-ethenylphenyl)-2-hydroxy-ethyl]cysteine (7). 2. In addition, minor metabolites, namely, 2-ethenylbenzoic acid (8) and 2-ethenylphenyl-acetic acid (9) were identified by glc-mass spectral analysis of the hydrolysed urine extract treated subsequently with diazomethane, hydroxylamine and a trimethyl-silylating reagent. Several compounds, which could arise from biotransformation of both ethenyl groups in the molecule of 1, were detected but not identified unequivocally. 3. A glucuronide was detected by tlc analysis of urine as a blue spot after spraying with naphthoresorcinol. Compounds showing molecular fragments indicating the glucuronide moiety were also detected by glc-mass spectroscopy in non-hydrolysed urine samples. 4. The total thioether excretion amounted to 5.3 +/- 2.4, 5.1 +/- 3.4 and 5.0 +/- 1.9% of the dose at 500, 300 and 100 mg/kg, respectively (mean +/- SD; n = 5). 5. Like styrene and other diethenylbenzene isomers, 1,2-diethenylbenzene is metabolically activated to a reactive epoxide intermediate, 2-ethenylphenyloxirane (10), which is further converted to the urinary metabolites mentioned above. The main detoxification pathways are hydrolysis to the glycol 2 followed by several oxidation steps, and conjugation with glutathione. The latter reaction is both regioselective and stereoselective. 6. The ratio of mercapturic acids 6:7 was 83:17. Each regioisomer consists of two diastereomers which show distinct resonance signals in the 13C-nmr. The diastereomer ratio was 82:28 and 79:21 for 6 and 7 respectively.

Ergot alkaloid glycosides with immunomodulatory activities

New glycosides derived from ergot alkaloids elymoclavine and DH-lysergol were synthesized by chemoenzymatic methods. beta-Glucosides were obtained either by chemical method or by transglycosylation (glycosidase from Aspergillus oryzae), lactosides were prepared by further extension of carbohydrate chain using beta-1,4-galactosyltransferase (bovine milk) and alpha-5-N-acetylneuraminyl-(2-->6)-beta-D-galactopyranosyl-(l-->4)-2- acetamido-2-deoxy-beta-D-glucopyranosyl-(1-->O)-elymoclavine was prepared using alpha-2,6-sialyltransferase (rat liver). Immunomodulatory activity of elymoclavine and 9,10-dihydrolysergol and their glycosylated derivatives on natural killer (NK) cell-mediated cytotoxicity of human resting and activated human peripheral blood mononuclear cells (PBMC) was investigated. Addition of ergot alkaloid glycosides to the mixtures of effector and target cells potentiated the PBMC cytotoxicity against both NK-sensitive and -resistant target cells. The glycoconjugates of elymoclavine enhanced cytotoxicity of PBMC against NK-resistant target cells. The glycoconjugates of DH-lysergol potentiated NK cytotoxicity of PBMC against NK-sensitive target cells.

N-1-Trimethylsilyl Derivatives of Ergot Alkaloids

N-1-Trimethylsilyl derivatives of five different suitably protected parent ergot (clavine) alkaloids (agroclavine 1a, elymoclavine 2a, lysergol 3a, lysergene 4a, and 9,10-dihydrolysergol 5a) were prepared in 47-94% yields by refluxing the (protected) parent compounds with N-methyl-N-(trimethylsilyl)trifluoroacetamide in acetonitrile under nitrogen atmosphere.

Titanium-Catalyzed [4+2] and [6+2] Cycloadditions of 1,4-Bis(trimethylsilyl)buta-1,3-diyne

The (C2H5)2AlCl/TiCl4 catalyst induces the [4+2] cycloaddition of butadiene or the [6+2] cycloaddition of 1,3,5-cycloheptatriene (CHT) to individual acetylenic moieties of 1,4-bis(trimethylsilyl)buta-1,3-diyne (BSD). Heating of the 2:1 butadiene adduct, bis(2-trimethylsilylcyclohexa-1,4-dien-1-yl), to 250 °C yields 2,2'-bis(trimethylsilyl)biphenyl. The 1:1 adduct of BSD with CHT, 7-trimethylsilyl-8-trimethylsilylethynylbicyclo[4.2.1]nona-2,4-diene, is obtained as virtually the only product if the initial molar ratio CHT : BD equal to 1.86 is used.

Electrophilic Substitution Reactions of [1]Benzothieno[3,2-b]furan

In chlorination, bromination, iodination, nitration, sulfonation, formylation, and trifluoroacetylation of [1]benzothieno[3,2-b]furan (1) the substituent enters the 2-position. The said halogenations go by the addition-elimination mechanism. When the substitution is continued, the second substituent enters the 6-position of heterocycle 1. The 1H and 13C NMR spectra have been completely assigned. Substituent effects on NMR parameters are discussed.

Fumaria densiflora DC. Alkaloids

Twenty isoquinoline alkaloids were identified in the aerial part of Fumaria densiflora DC. In addition to bicuculline, densiflorine, fumaritine, fumariline, scoulerine, coptisine, cryptopine, parfumine, protopine, and sinactine which have been found previously, the following alkaloids were isolated for the first time from this species: adlumine, fumaricine, fumaritridine, fumarophycine, fumarofine, corytuberine, cis-N-methylstylopinium iodide, stylopine, and two new 1-benzylisoquinoline alkaloids, viz. fumaflorine and fumaflorine methyl ester. The cytoprotectivity of extracts of F. densiflora and F. officinalis, and that of protopine, cryptopine, and parfumine was tested on primary cultures of rat hepatocytes intoxicated with carbon tetrachloride. The cytoprotective effect of the extracts is associated with the alkaloids.

N-(2-Methyl-2-nitropropyl) and N-Nitroso Derivatives of Some Diamines

Preparation of ten new derivatives of 1,6-hexanediamine and 1,4-bis(4-aminophenoxy)butane with different combination of N-nitroso and/or N-(2-methyl-2-nitropropyl) groups is presented. The title compounds are potential improvers of vulcanized rubber dynamic properties.

BF3-catalysed methanolysis combined with fast atom bombardment tandem mass spectrometry as a new tool for the preparation and analysis of linear secocyclosporins

BF3-catalysed methanolysis is presented for cyclic peptide cleavage using cyclosporins as model compounds. The reaction conditions for BF3-catalysed methanolysis of cyclosporins were optimized to favour the formation of linear undecapeptides. The resulting secocyclosporins were analysed by fast atom bombardment tandem mass spectrometry. Only one dominant and two side mechanisms of the ring opening are operating so that the complete sequence determination of all prepared oligopeptides was achieved.

Cyclosporins from Tolypocladium terricola

New natural cyclosporins were isolated from the mycelium of surface cultivated fungus Tolypocladium terricola. The chemical structures of [Leu4] CS and [MeLeu1] CS = cyclosporin-J, were deduced from the NMR and mass spectral data. Biological activity of new cyclosporins is reported based on the proliferative mitogen stimulation test.

Beauverolides L and La from Beauveria tenella and Paecilomyces fumosoroseus

New beauverolides L and La were isolated and identified from the entomopathogenic fungi, Beauveria tenella and Paecilomyces fumosoroseus. Their structures, cyclo-[3-hydroxy-4-methyldecanoyl-L-phenylalanyl-L-alanyl-D-leucyl ], and cyclo-[3-hydroxy-4-methyldecanoyl-L-phenylalanyl-L-alanyl-D-allo-i soleucyl] were deduced from HPLC and GC-mass spectrometric analyses of their hydrolysates and NMR and mass spectral data.

Production of 26-deoxymonensins A and B by Streptomyces cinnamonensis in the presence of Metyrapone

Metyrapone, a potent cytochrome P-450 inhibitor, added at 9 mM to a submerged culture of Streptomyces cinnamonensis caused partial inhibition of total monensin biosynthesis and coproduction of new metabolites, 26-deoxymonensins A and B. The latter was isolated as its 25-O-methyl derivative. Metyrapone was simultaneously reduced to metyrapol. All of these compounds were identified by nuclear magnetic resonance spectroscopy and mass spectrometry.

2,3-Dihydro-2-oxoergolene Derivatives

A general procedure for the preparation of 2-oxo derivatives of 8- or 9-ergolene is reported. Mass and NMR spectra of these compounds are discussed.

Biosynthesis of destruxins

L-[Me-13C]-Methionine, sodium [2-13C]acetate and sodium [1,2-13C]acetate were incorporated into destruxins A, B and E by the entomopathogenic fungus Metarhizium anisopliae. NMR analysis established that methionine is involved in the N-methylation of L-valine and L-alanine, and that one intact acetate unit participates in the biosynthesis of the -CH(OH)-COOH fragment of the hydroxy acid moiety. The presence of two acetate units in proline and isoleucine agrees with the accepted biochemical schemes.