R. S. Borisov

Concise approach toward tetrazolo[1,5-a][1,4]benzodiazepines via a novel multicomponent isocyanide-based condensation.

A novel and efficient method for the synthesis of heteroannulated [1,4]benzodiazepines via an isocyanide-based multicomponent reaction is reported. The tetrazolo[1,5-a][1,4]benzodiazepines were obtained by a facile azide Ugi five-center four-component reaction (U-5C-4CR) using ketones, sodium azide, ammonium chloride, and corresponding isocyanide. The aforementioned tetrazolodiazepines represent a notable class of compounds with proven platelet aggregation inhibitory and cholecystokinin agonist activities.

A general strategy for the synthesis of oxoisoindolo[2,1-a]quinoline derivatives: the first efficient synthesis of 5,6,6a,11-tetrahydro-11-oxoisoindolo[2,1-a]quinoline-10-carboxylic acids

An efficient two-step synthesis of new isoindolo[2,1-a]quinoline-10-carboxylic acids via [4+2] cycloaddition of the 4-α-furyl-4-N-arylaminobut-1-enes and maleic anhydride is described.

Derivatization aids in the determination of end groups in poly(alkylene glycol)s by matrix-assisted laser desorption/ionization mass spectrometry.

A method for end-group characterization by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry following preliminary derivatization with N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) and capryloyl chloride is described and applied to poly(alkylene glycol)s. The MALDI mass spectra of the products revealed peaks of sodiated derivative cations, whose shift by the respective increments allowed the determination of the number of end functional groups with active hydrogens. This approach is particularly efficient for the distinction of cyclic and linear dehydration products among minor components.

Chromatographic-mass spectrometric analysis of Fischer-Tropsch synthesis products

The products of Fischer–Tropsch synthesis were comprehensively analyzed by chromatography–mass spectrometry using the AMDIS software and the NIST/EPA/NIH mass spectral database. Structures of more than 90% of the major components were established, and their retention indices and quantitative concentrations in the mixture were determined.

Preliminary silylation for structure determination of oligomeric silsesquioxanes by matrix- assisted laser desorption/ionisation mass spectrometry.

The potential of preliminary silylation for the determination of numbers of hydroxyl groups in separate molecules of oligomeric silsesquioxanes by matrix-assisted laser desorption/ionisation mass spectrometry has been demonstrated for the first time. Derivatisations allowing the introduction of trimethylsilyl, tert-butyldimethylsilyl and pentafluorophenyldimethylsilyl groups were tested. It was shown that more reliable structure elucidation of individual oligomers can be achieved knowing the number of hydroxyl groups thus determined.

Eugenol derivatives of higher chlorocyclophosphazenes and related epoxy oligomers

The synthesis of eugenol derivatives of octachlorocyclotetraphosphazene and mixtures of oligomer chlorocyclophosphazenes [NPCl2]3–8 was performed. Not yet described octakis(4-allyl-2-methoxyphenoxy)cyclotetraphosphazene was isolated in the crystalline form and identified via 31P and 1H NMR spectroscopy, laser mass spectrometry, DSC, and TGA. Oligomers with epoxy numbers of 15–16% and molecular masses from 1400 to 1800 were prepared via epoxidation of the synthesized eugenol derivatives with m-chloroperbenzoic acid. Some assumptions on the nature of side reactions occurring in the course of epoxidation were made.

Reactive matrices for matrix-assisted laser desorption/ionization mass spectrometry of primary amines

Some aromatic carbonyl compounds [2,4-dihydroxybenzaldehyde (2,4-DHBA), 2,5-dihydroxyacetophenone (DHAP), 2,3,5-trihydroxybenzaldehyde and 2,4-dinitrobenzaldehyde] were examined as potential reactive matrices for the analysis of mono-, di-, and polyamines by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS). Although all the above compounds readily and quantitatively react with primary amines to form Schiff bases (the completeness of the reactions was proved by gas chromatography MS of derivatized aliphatic amines), only DHBA and DHAP provide efficient desorption/ionization under MALDI conditions. This means that two these aromatic carbonyl compounds can simultaneously exhibit properties of both derivatization agents and efficient matrices for MALDI-MS analysis. The use of such reactive matrices eliminates the need to perform additional derivatization experiments. With the aid of DHBA and DHAP, it was confirmed that each individual oligomer of polypropylene glycols and co-polyethylene/propylene glycols contained two terminal amino groups. To calculate the number of NH2 groups, mass increments of the introduced groups and a difference in the masses of cations attached to the initial and derivatized amines were used. The suggested approach, involving the application of the same reactive matrices, was applied to the determination of a number of NH2 groups in individual oligomers of branched polyethyleneimines (PEIs) by MALDI-MS. In this case, DHAP appeared to be the best reactive matrix. The dependence of the number of NH2 groups on the quantity of monomeric units and branching of each individual PEI oligomer is shown.

Synthesis and modification of oligo(aryloxycyclotriphosphazenes) based on 4,4′-dihydroxydiphenyl-2,2-propane

Oligo(aryloxyphosphazenes) are synthesized on the basis of diphenylolpropane and hexachlorocyclotriphosphazene via the phenolate method. Corresponding functional derivatives are obtained through treatment of the oligomers with methacryloyl chloride, glycidyl methacrylate, and epichlorohydrin. GPC data indicate that modification is accompanied by an increase in the molecular mass of the oligomers. Epoxidation of a specially synthesized hexaallyloxy derivative of oligo(aryloxycyclotriphosphazene) with m-chloroperbenzoic acid proceeds incompletely to yield an oligomer with a content of epoxy groups below 6%. All of the compounds are characterized with the use of 31P and 1H NMR spectroscopy.

Derivatization of synthetic polymers in mass spectrometric studies

The review describes various derivatization approaches employed for the investigation of synthetic polymers by mild ionization mass spectrometry (fast atom and ion bombardment, matrix-assisted laser desorption/ionization, electrospray/ionization). The potentials of chemical methods for modification of end- and side-chain functional groups without the decomposition of molecules are demonstrated. Methods of the preliminary chemical degradation of polymer molecules for the investigation of their microstructure are considered. The possibilities of the chemical modification of polymer surfaces for the identification and quantitative determination of functionalized fragments are shown.

Simple approach to derivatization of alcohols and phenols for the analysis by matrix(surface)‐assisted laser desorption/ionization time‐of‐flight mass spectrometry

RATIONALE Direct analysis of hydroxyl-containing compounds by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS) methods is not always possible due to the neutral character of analytes. The suggested fixed-charge derivatization may increase the ionization efficiency for various alcohols and phenols in specific matrix- and surface-activated LDI conditions. METHODS Aliphatic and steroid alcohols, as well as chlorophenols, were converted into various ammonioacetyl derivatives, containing a covalently bonded charged group, by reaction with bromoacetyl chloride and amine-type compounds such as triethylamine, pyridine or quinoline. The derivatives are suitable for MALDI-time-of-flight (TOF)MS analysis. RESULTS Triethylammoniumacetyl, pyridyliumacetyl and quinoliniumacetyl derivatives were prepared from aliphatic alcohols, some sterols and chlorinated phenols in one stage with quantitative yields. The derivatives produced characteristic MALDI and SALDI mass spectra. CONCLUSIONS The suggested derivatization approach for the modification of alcohols is simple and does not require any expensive reagents. The derivatives include a fixed charge and produce intense signals in MALDI (preferentially non-acidic matrices) and matrix-free SALDI (nanostructured target) conditions. Corresponding mass spectra are suitable for the determination of molecular mass and profiling of alcohols.