Coupling of fully automated chip electrospray to Fourier transform ion cyclotron resonance mass spectrometry for high-performance glycoscreening and sequencing

The NanoMate robot has been coupled to a Fourier transform ion cyclotron resonance (FTICR) mass spectrometer at 9.4 T and implemented for the first time for complex carbohydrate analysis. It was optimized in the negative ion mode to achieve automated sample delivery on the chip along with increased sensitivity, ultra-high resolution and accurate mass determination. A novel bracket has been designed to allow a reliable mounting of the NanoMate to the Apollo electrospray ionization (ESI) source of an APEX II instrument. The notably higher efficiency of ionization for compositional mapping of complex mixtures and feasibility for fragmentation analysis of components by sustained off-resonance irradiation collision-induced tandem mass spectrometry (SORI-CID MS2) has been demonstrated on a glycoconjugate mixture containing O-glycosylated sialylated peptides from urine of a patient suffering from a hereditary N-acetylhexosaminidase deficiency (Schindler's disease), previously analyzed by capillary-based nanoESI-FTICRMS, and of a healthy control person. Due to its potential to generate highly charged ionic species, reduce the in-source fragmentation, increase sensitivity, reproducibility and ionization efficiency, along with the ability to generate a sustained and constant electrospray, this method can be considered as a new platform for advanced glycomics.     

Chemical and photochemical synthesis of substituted dihydro-thieno[2',3':4,5]thieno[2,3-c]quinolin-6-ones and tetrahydro-dithieno[2,3-b:2',3'-d]thieno[2'',3''c:2'',3''c']diquinolin-6,14-dione

Some new substituted dihydrothieno[2',3':4,5]thieno[2,3-c]quinolin-6-ones 9- 12 and tetrahydrodithieno[2,3-b: 2',3'-d]thieno[2',3'-c:2',3'-c']diquinolin-6,14-dione (17) were prepared from the corresponding new anilides 5-8 and from the corresponding dianilide 15, respectively, by a multistep combination of chemical and photochemical reactions. All the prepared compounds are of particular interest because they might serve as DNA intercalators in anticancer therapy.     

Säurekatalysierte Umlagerung von 4-Allyl-cyclohex-2-en-1-olen; Beispiele für ladungskontrollierte [3s, 4s]-Umlagerungen von cyclischen Allylkationen

The acid-catalysed rearrangement of the cyclohex-2-en-1-ols 15 , d₃- 15 , 16 , 17 and 19 , the cyclohexa-2,5-dien-1-ols 20 and 21 , and also the allyl alcohols 22 and 23 (Scheme 3), using 98-percent sulfuric acid/acetic anhydride 1:99 at room temperature, was investigated. From the rearrangement of 4-allyl-4-phenyl-cyclohex-2-en-1-ol ( 15 ), with reaction times greater than 2 hours a single product is obtained, 4-allyl-biphenyl ( 50 ) in 33% yield (Scheme 9). With reaction times below 2 hours the acetate 53 from 15 was isolated, and this could be converted into 50 . The reaction of 2′,3′,3′-d₃-15 in Ac₂O/H₂SO₄ lead to 1′,1′,2′-d₃-50 (Scheme 11). The rearrangement of 4-allyl-4-methyl-cyclohex-2-en-1-ol (16) (Scheme 14) yielded 39% of the corresponding acetate 60 and 30% of 4-allyl-toluene ( 6 ), which also resulted by a rearrangement of 60 under the reaction conditions. These rearrangements are all [3s,4s]-sigmatropic reactions, which proceed via the cyclohexenyl cation a (Scheme 12, R = C₆H₅, CH₃). In Ac₂O/H₂SO₄ the allyl-cyclohexadienes primarely formed subsequently undergo dehydrogenation to yield the benzene derivatives 6 , 50 and d₃- 50 . From the rearrangement of 4,4-diphenyl-cyclohex-2-en-1-ol ( 19 ) at 0° a reaction mixture is obtained which consists of the acetate 55 , 2,3-diphenyl-cyclohexa-1,4-diene ( 57 ) and o-terphenyl ( 56 ) (Scheme 10). Both 55 and 57 are converted under the reaction conditions to o-terphenyl ( 56 ). No 4-(1′-methylallyl)-biphenyl is obtained from the rearrangement of 4-crotyl-4-phenyl-cyclohex-2-en-1-ol ( 17 ). In this case, apart from the corresponding acetate 64 , a single product 5-(1′-acetoxyethyl)-1-phenyl-bicyclo[2.2.2]oct-2-ene ( 65 ) (Scheme 16) was obtained; under the reaction conditions the acetate 64 rearranges to 65 . The rearrangement of 4-allyl-4-phenyl-cyclohexa-2,5-dien-1-ol ( 20 ) gives, as expected, not only 4-allyl-biphenyl ( 50 ) but also 2- and 3-allyl-biphenyl ( 51 and 52 ) and biphenyl (Scheme 13). 4-Benzyl-4-methyl-cyclohexa-2,5-dien-1-ol (syn- and anti- 21 ) gave in Ac₂O/H₂SO₄ at 10° as rearrangement products 93% of 2-benzyltoluene ( 97 ) and 7% of 4-benzyl-toluene ( 98 ) (Scheme 21). Hence [1,4]-rearrangements in cyclohexadienyl cations, seems to occur only to a limited extent. The alicyclic alcohols 22 and 23 (Scheme 18) gave, in Ac₂O/H₂SO₄, as main product the corresponding acetates 73 and 75 , as well as small amounts of olefins 74 and 76 formed by dehydration i.e. [3,4]-rearrangements occur in these systems. Also no [3,4]-rearrangements were observed in solvents reactions of either 4,4-dimethyl-hepta-1, 6-dien-3-yl tosulate (79; see Scheme 19) or its corresponding alcohol 24.     

Applications of SHAPES screening in drug discovery

The SHAPES strategy combines nuclear magnetic resonance (NMR) screening of a library of small drug-like molecules with a variety of complementary methods, such as virtual screening, high throughput enzymatic assays, combinatorial chemistry, X-ray crystallography, and molecular modeling, in a directed search for new medicinal chemistry leads. In the past few years, the SHAPES strategy has found widespread utility in pharmaceutical research. To illustrate a variety of different implementations of the method, we will focus in this review on recent applications of the SHAPES strategy in several drug discovery programs at Vertex Pharmaceuticals.     

Synthesis of some schiff bases of 3-aroyl-6-aryl-4-hydroxy-2H-pyran-2-ones

Summary The reaction of 3-aroyl-6-aryl-4-hydroxy-2H-pyran-2-ones (Ar=p-tolyl, 1,1-biphenyl-4-yl or thienyl) with aniline and substitutedo-phenylenediamine (R=H, CH₃ or Cl) yields a series of new Schiff bases2a–f in 51–72% yield. Bromination of1a gave the 5-bromo derivative1c, while the compounds1a,1b,2b,2e, and2f were converted into 2,6-diaryl-4H-pyran-4-ones3a–c. All products have been fully characterized.

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Synthese von Schiff'schen Basen von 3-Aroyl-6-aryl-4-hydroxy-2H-pyran-2-onen

Zusammenfassung Die Reaktion von 3-Aroyl-6-aryl-4-hydroxy-2H-pyran-2-onen (Ar=p-Tolyl, 1,1-Biphenyl-4-yl oder Thienyl) mit Anilin und substituierteno-Phenylendiaminen liefert neue Schiff'sche Basen2a–f/bd in 51–72% Ausbeute. Bromierung von1a gab das 5-Bromderivate1c, während die Verbindungen1a,1b,2b,2e und2f in 2,6-Diaryl-4H-pyran-4-onen3a–c übergeführt wurden. Alle Produkte wurden voll charakterisiert.

     

Precipitation of radiation belt electrons by magnetospherically reflected (MR) whistlers

We use a test particle simulation model based on gyro-averaged equations of motion to study the influence of oblique magnetospherically reflected (MR) whistlers on the near-loss-cone distribution function of radiation belt electrons. We find that MR whistlers originating in lightning can resonantly interact with radiation belt electrons over a broad range of L-shells and precipitate higher energy electrons from lower L-shells. Electrons in the energy range of 1–2.6 MeV are precipitated from L=2, whereas from L=4 the precipitated electron energy range is 150–220 keV. The precipitated differential electron flux due to this interaction is higher for higher L-shells, and the maximum value ranges from at at L=4. The lifetimes of radiation belt electrons in a given magnetic flux tube around the L-shell on which the interaction takes place are found to be of the order of several days, comparable to lifetimes corresponding to electron loss induced by hiss, which was heretofore assumed to be the dominant loss mechanism [1]. The minimum electron lifetimes vary from 2.47 days for E=1.11 MeV electrons at L=2 to 4.64 days for E=173 keV electrons at L=4.LOLA Research Center, Belgrade, Yugoslavia. STAR Laboratory, Stanford University, Stanford, California. Published in Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 37, No. 6, pp. 727–740, June, 1994.     

A method for constructing diabatic states by interpolation on the reduced density matrix

Avoided crossing of adiabatic potential energy curves is considered. A new scheme for the adiabatic-diabatic transformation is developed that is based on an interpolation performed on reduced one-electron density matrices. The procedure is tested on the N₂ molecule.     

Granular dynamics in compaction and stress relaxation

Elastic and dissipative properties of granular assemblies under uniaxial compression are studied both experimentally and by numerical simulations. Following a novel compaction procedure at varying oscillatory pressures, the stress response to a step strain reveals an exponential relaxation followed by a slow logarithmic decay. Simulations indicate that the latter arises from the coupling between damping and collective grain motion predominantly through sliding. We characterize an analogous "glass transition" for packed grains, below which the system shows aging in time-dependent sliding correlation functions.     

Enantiomers and barriers to racemization of sterically hindered N-aryl- and N-heteroarylpyrroles

The N-aryl- and N-heteroaryl-2,5-dimethylpyrrole-3-carbaldehydes 2–8 have been synthesized by condensation of hexane-2,5-dione with the appropriate amine and subsequent Vilsmeier-Haack formylation of the pyrrole ring. Diastereomeric association complexes of the racemic pyrrole 8 were studied by pmr chemical shifts and the splittings induced by (+)-1-(9-anthryl)-2,2,2-trifluoroethanol. Enrichment of the enantiomers M and P of 2 and 6 was achieved by liquid chromatography on triacethylcellulose. The barrier to partial rotation about the C-N bond in 6 was determined by thermal racemization and its lower limits in 2 and 8 were estimated.     

Reply to the comment on the energy variation method

The assertion that the energy variation theorem for excited states follows from the classical minmax principle is further reinforced. The problem of minimizing the manifold energy in the non-orthogonal basis is also solved.