Effect of the location of hydrogen abstraction on the fragmentation of diuretics in negative electrospray ionization mass spectrometry.

The diuretic agents bumetanide, xipamide, indapamide, and related compounds were investigated in order to determine the effect of different ionization sites on their collisionally activated dissociation and the corresponding fragmentation pathways. Therefore, analytes were selectively alkylated, and structural analogues as well as deuterium labeled compounds synthesized, which contain a reduced number of ionizable hydrogen atoms. Thus, specific hydrogen abstractions and their correlated dissociation routes of the negatively charged molecules were eliminated, providing evidence for the influence of the location of ionization on product ion spectra.

Mass spectrometry of steroid glucuronide conjugates. II-Electron impact fragmentation of 3-keto-4-en- and 3-keto-5alpha-steroid-17-O-beta glucuronides and 5alpha-steroid-3alpha,17beta-diol 3- and 17-glucuronides.

The steroid glucuronide conjugates of 16,16,17-d(3)-testosterone, epitestosterone, nandrolone (19-nortestosterone), 16,16,17-d(3)-nortestosterone, methyltestosterone, metenolone, mesterolone, 5alpha-androstane-3alpha,17beta-diol, 2,2,3,4,4-d(5)-5alpha-androstane-3alpha,17beta-diol, 19-nor-5alpha-androstane-3alpha,17beta-diol, 2,2,4,4-d(4)-19-nor-5alpha-androstane-3alpha,17beta-diol and 1alpha-methyl-5alpha-androstane-3alpha/beta,17beta-diol were synthesized by means of the Koenigs-Knorr reaction. Selective 3- or 17-O-conjugation of bis-hydroxylated steroids was performed either by glucuronidation of the corresponding steroid ketole and subsequent reduction of the keto group or via a four-step synthesis starting from a mono-hydroxylated steroid including (a) protection of the hydroxy group, (b) reduction of the keto group, (c) conjugation reaction and (d) removal of protecting groups. The mass spectra and fragmentation patterns of all glucuronide conjugates were compared with those of the commercially available testosterone glucuronide and their characterization was performed by gas chromatography/mass spectrometry and nuclear magnetic resonance spectroscopy.

Mass spectrometry of steroid glucuronide conjugates. I. Electron impact fragmentation of 5alpha-/5beta-androstan-3alpha-ol-17-one glucuronides, 5alpha-estran-3alpha-ol-17-one glucuronide and deuterium-labelled analogues.

Owing to the developments of analytical instruments and interfaces (e.g. coupling high-performance liquid chromatography to mass spectrometry), there has been increased interest in new reference materials, for example in doping analysis with steroid glucuronide conjugates.

Further isoflavonoid metabolites from Millettia griffoniana (Bail).

Three new isoflavonoids, griffonianone A (1), B (2) and C (4) were isolated from the root bark of Millettia griffoniana, along with the known maximaisoflavone G (5) and 7-hydroxy-6-methoxy-3',4'-methylenedioxyisoflavone (6). Their structures were assigned on the basis of spectroscopic data and chemical transformations.

A pyoverdin from Pseudomonas sp. CFML 95-275.

From Pseudomonas sp. CFML 95-275 a pyoverdin was isolated with a cyclopeptidic substructure. It could be shown that this pyoverdin is identical with one obtained from Pseudomonas fluorescens BTP 7 for which a lactone structure had been deduced from the interpretation of a FAB spectrum.

Photocyclization of 2-azabicyclo[3.3.0]octane-3-carboxylate derivatives: induced and noninduced diastereoselectivity.

[reaction: see text] The decarboxylative photocyclization of potassium 2-azabicyclo[3.3.0]octanoate ethylene-linked to phthalimide leads to a mixture of two diastereoisomeric products.

Photoinduced electron-transfer reactions with quinolinic and trimellitic acid imides: experiments and spin density calculations(1).

The regioselectivity of photoinduced electron-transfer (PET) reactions of unsymmetrical phthalimides is controlled by the spin density distribution of the intermediate radical anions. ROHF ab initio calculations were found to be most suitable for atomic spin density analysis. Intramolecular PET reactions of quinolinic acid imides were studied with the potassium butyrate and hexanoate 1a,b and a cysteine derivative 3.

Competitive formation of helical cycloocta- and cyclododecapyrroles.

In connection with a study aimed at the evaluation of electronic effects in spiro-dicorrole (1a) and its binuclear Ni(II) complex (1b) we became interested in gem-dimethyl-substituted cyclotetrapyrrole (2a) and the corresponding Ni(II) complex (2b). Attempts to prepare 2a as the 12,13,16,17-tetraethyl-2,3,7, 8-tetramethyl derivative (5) by an acid-catalyzed (1 + 1) condensation of dimethyldipyrrylmethane 3 and diformylbipyrrole 4 resulted in the formation of the (2 + 2) and (3 + 3) condensation products, i.e.

Isoporphycene: The Fourth Constitutional Isomer of Porphyrin with an N(4) Core-Occurrence of E/Z Isomerism.

Liberation of the ligand from the nickel complex 1 obtained by template synthesis yielded isoporphycene (as the octaethyl derivative 2), the first constitutional isomer of porphyrin with an N(4) core for which E/Z isomerism is involved: Compound 2 is present as the E isomer, which is in rapid, presumably acid-catalyzed equilibrium with a small amount (2 %) of the Z isomer. The remaining unknown constitutional isomers of porphyrin are considerably higher in energy than the already rather labile isoporphycene, so that the latter should mark the border of existence for this type of structural variant of porphyrin.