Synthesis of polysubstituted pyrroles via [3 + 2]-annulation of aziridines and β-nitroalkenes under aerobic conditions

Polysubstituted pyrroles are regioselectively synthesizedviathe copper acetate-catalyzed [3 + 2] annulation reaction of aziridines and nitroalkenes under aerobic conditions.

AlCl3-promoted [3 + 2] annulation of cis-2,3-disubstituted cyclopropane 1,1-diesters with isothiocyanates: stereoselective synthesis of densely substituted 2-iminodihydrothiophenes

cis-2,3-Disubstituted cyclopropane 1,1-diesters were found to be much more reactive than their corresponding trans-isomers in the AlCl3-promoted [3 + 2]-annulations with isothiocyanates. The reaction with the cis-cyclopropanes proceeded to completion within minutes, providing a variety of densely substituted diastereomerically pure 2-iminodihydrothiophenes in moderate to excellent yields.

A novel Lewis acid catalyzed [3 + 3]-annulation strategy for the syntheses of tetrahydro-β-carbolines and tetrahydroisoquinolines

A novel Lewis acid catalyzed [3 + 3]-annulation process for the efficient syntheses of both tetrahydro-β-carbolines and tetrahydroisoquinolines from readily available benzylic alcohols and aziridines was developed, which would be a highly valuable complement to the widely used Pictet-Spengler reaction. A probable mechanism was proposed based on the isolation and characterization of two key intermediates. This strategy enables facile access to important alkaloid frameworks not easily available with other known methods.

Chiral Brønsted acid-catalyzed diastereo- and enantioselective synthesis of CF3-substituted aziridines

A multicomponent organocatalyzed highly diastereo- and enantioselective synthesis of CF(3)-substituted aziridines is described. This reaction of in situ generated CF(3)CHN(2) and aldimines was realized by chiral Brønsted acid catalysis. The utility of the products is illustrated by easy access to β-CF(3) isocysteine and aziridine-containing dipeptides.

Highly enantioselective [4 + 2] cycloadditions of allenoates and dual activated olefins catalyzed by N-acyl aminophosphines

An asymmetric organocatalytic [4 + 2] cycloaddition between α-substituted allenoates and dual activated olefins using bifunctional N-acyl aminophosphine catalysts is described. The use of 2-cyano acrylate derived olefins led to the first successful incorporation of an electrophile derived from an aliphatic aldehyde into this reaction.

Pd(II)/Brønsted acid catalyzed enantioselective allylic C-H activation for the synthesis of spirocyclic rings

A Pd(II)/Brønsted acid catalyzed migratory ring expansion for the synthesis of indene derivatives possessing a stereogenic spirocyclic carbon center was developed. This transformation is believed to mechanistically proceed via enantioselective allylic C-H activation with concomitant semipinacol ring expansion to the nascent π-allylpalladium species. Enantioselectivities as high as 98% ee were attainable.

Event-by-event fluctuations of azimuthal particle anisotropy in Au+Au collisions at square root(sNN) = 200 GeV

This Letter presents the first measurement of event-by-event fluctuations of the elliptic flow parameter v(2) in Au+Au collisions at square root(s(NN))=200 GeV as a function of collision centrality. The relative nonstatistical fluctuations of the v(2) parameter are found to be approximately 40%. The results, including contributions from event-by-event elliptic flow fluctuations and from azimuthal correlations that are unrelated to the reaction plane (nonflow correlations), establish an upper limit on the magnitude of underlying elliptic flow fluctuations. This limit is consistent with predictions based on spatial fluctuations of the participating nucleons in the initial nuclear overlap region. These results provide important constraints on models of the initial state and hydrodynamic evolution of relativistic heavy ion collisions.

High transverse momentum triggered correlations over a large pseudorapidity acceptance in Au + Au collisions at square root(s(NN)) = 200 GeV

A measurement of two-particle correlations with a high transverse momentum trigger particle (p(T)(trig) > 2.5 GeV/c) is presented for Au+Au collisions at square root(s(NN)) = 200 GeV over the uniquely broad longitudinal acceptance of the PHOBOS detector (-4 < Delta eta < 2). A broadening of the away-side azimuthal correlation compared to elementary collisions is observed at all Delta eta. As in p+p collisions, the near side is characterized by a peak of correlated partners at small angle relative to the trigger particle. However, in central Au+Au collisions an additional correlation extended in Delta eta and known as the "ridge" is found to reach at least |Delta eta| approximately = 4. The ridge yield is largely independent of Delta eta over the measured range, and it decreases towards more peripheral collisions. For the chosen (p(T)(trig) cut, the ridge yield is consistent with zero for events with less than roughly 100 participating nucleons.

Cell division autoantigen 1 plays a profibrotic role by modulating downstream signalling of TGF-beta in a murine diabetic model of atherosclerosis

AIMS/HYPOTHESIS

Excess accumulation of vascular extracellular matrix (ECM) is an important pathological process in cardiovascular diseases including diabetes-associated atherosclerosis. We explored how a recently identified molecule, cell division autoantigen 1 (CDA1), influences the profibrotic TGF-beta pathway leading to vascular ECM accumulation.

METHODS

Expression levels of genes encoding for CDA1, TGF-beta and connective tissue growth factor (CTGF) were examined in aorta from Apoe(-/-) mice with or without diabetes. We used retroviral and adenoviral constructs to knockdown or overexpress Tspyl2, the gene encoding CDA1, in mouse vascular smooth muscle cells (VSMCs) with or without TGF-beta treatment in order to demonstrate the role of CDA1 in TGF-beta signalling.

RESULTS

In vivo studies indicated that the mRNA levels of CDA1-encoding gene Tspyl2 and protein levels of CDA1 were elevated in the aorta of diabetic Apoe(-/-) mice, accompanied by increased levels of Tgf-beta (also known as Tgfb1), Ctgf and ECM accumulation. In vitro studies in vascular cells showed that TGF-beta treatment rapidly increased CDA1 protein levels, which then amplified TGF-beta signalling leading to upregulation of ECM genes. Knockdown of CDA1-encoding gene Tspyl2 to reduce cellular CDA1 level markedly attenuated TGF-beta-stimulated MAD homologue 3 (drosophila; SMAD3) phosphorylation and transcriptional activities. CDA1 overproduction increased and Tspyl2 knockdown decreased expression of TGF-beta receptor type I, TbetarI (also known as Tgfbr1), but not TGF-beta receptor type II, TbetarII (also known as Tgfbr2), providing a mechanism for CDA1's action in modulating TGF-beta signalling. Knockdown of CDA1-encoding gene Tspyl2 also blocked the profibrotic effect of TGF-beta in VSMCs.

CONCLUSIONS/INTERPRETATION

CDA1 plays an important role in vascular ECM accumulation by amplifying TGF-beta signalling. This is critical for the profibrotic effect of TGF-beta in the vasculature. CDA1 is therefore a potential target for attenuating vascular ECM accumulation caused by enhanced TGF-beta action, as seen in diabetic atherosclerosis.

Highly enantio- and diastereoselective synthesis of alpha-trifluoromethyldihydropyrans using a novel bifunctional piperazine-thiourea catalyst

The first enantioselective Michael addition of alpha-cyanoketones to alpha,beta-unsaturated trifluoromethyl ketones using a novel piperazine-thiourea catalyst was described. The resulting alpha-trifluoromethyldihydropyrans were obtained in high yields and with up to 95% ee within a short reaction time. A useful transformation of the chiral adduct was also illustrated.

Facile stereoselective synthesis of fluorinated flavanone derivatives via a one-pot tandem reaction

A series of fluorinated flavanones were synthesized in moderate to good yields with excellent diastereoselectivities under mild reaction conditions via a one-pot tandem procedure involving a proline-catalyzed Knoevenagel condensation, a Michael addition, and an electrophilic fluorination by NFSI.

System size, energy, and centrality dependence of pseudorapidity distributions of charged particles in relativistic heavy-ion collisions

We present the first measurements of the pseudorapidity distribution of primary charged particles in Cu+Cu collisions as a function of collision centrality and energy, sqrt[s_{NN}]=22.4, 62.4, and 200 GeV, over a wide range of pseudorapidity, using the PHOBOS detector. A comparison of Cu+Cu and Au+Au results shows that the total number of produced charged particles and the rough shape (height and width) of the pseudorapidity distributions are determined by the number of nucleon participants. More detailed studies reveal that a more precise matching of the shape of the Cu+Cu and Au+Au pseudorapidity distributions over the full range of pseudorapidity occurs for the same N{part}/2A rather than the same N_{part}. In other words, it is the collision geometry rather than just the number of nucleon participants that drives the detailed shape of the pseudorapidity distribution and its centrality dependence at RHIC energies.

3He spin-dependent cross sections and sum rules

We present a measurement of the spin-dependent cross sections for the 3He over -->(e over -->,e')X reaction in the quasielastic and resonance regions at a four-momentum transfer 0.1< or =Q2< or =0.9 GeV2. The spin-structure functions have been extracted and used to evaluate the nuclear Burkhardt-Cottingham and extended Gerasimov-Drell-Hearn sum rules for the first time. The data are also compared to an impulse approximation calculation and an exact three-body Faddeev calculation in the quasielastic region.

Et2Zn-catalyzed intramolecular hydroamination of alkynyl sulfonamides and the related tandem cyclization/addition reaction

Intramolecular hydroamination of alkynyl amides was effected by a catalytic amount of Et2Zn (20 mol %) to form indole derivatives, and a tandem cyclization/nucleophilic addition procedure involving reaction of the indole zinc salt intermediate with acid chlorides or halides was developed to provide an efficient approach to C3-substituted indole derivatives when an excess of Et2Zn (120 mol %) was used.

System size, energy, pseudorapidity, and centrality dependence of elliptic flow

This Letter presents measurements of the elliptic flow of charged particles as a function of pseudorapidity and centrality from Cu-Cu collisions at 62.4 and 200 GeV using the PHOBOS detector at the Relativistic Heavy Ion Collider. The elliptic flow in Cu-Cu collisions is found to be significant even for the most central events. For comparison with the Au-Au results, it is found that the detailed way in which the collision geometry (eccentricity) is estimated is of critical importance when scaling out system-size effects. A new form of eccentricity, called the participant eccentricity, is introduced which yields a scaled elliptic flow in the Cu-Cu system that has the same relative magnitude and qualitative features as that in the Au-Au system.

Energy dependence of directed flow over a wide range of pseudorapidity in Au + Au collisions at the BNL Relativistic Heavy Ion Collider

We report on measurements of directed flow as a function of pseudorapidity in Au + Au collisions at energies of square root of SNN = 19.6, 62.4, 130 and 200 GeV as measured by the PHOBOS detector at the BNL Relativistic Heavy Ion Collider. These results are particularly valuable because of the extensive, continuous pseudorapidity coverage of the PHOBOS detector. There is no significant indication of structure near midrapidity and the data surprisingly exhibit extended longitudinal scaling similar to that seen for elliptic flow and charged particle pseudorapidity density.

System size and centrality dependence of charged hadron transverse momentum spectra in Au + Au and Cu + Cu collisions at square root of SNN = 62.4 and 200 GeV

We present transverse momentum distributions of charged hadrons produced in Cu + Cu collisions at square root of SNN = 62.4 and 200 GeV. The spectra are measured for transverse momenta of 0.25 < pT < 5.0 GeV/c at square root of SNN = 62.4 GeV and 0.25 < pT < 7.0 GeV/c at square root of SNN = 200 GeV, in a pseudorapidity range of 0.2 < eta < 1.4. The nuclear modification factor R(AA) is calculated relative to p + p data at both collision energies as a function of collision centrality. At a given collision energy and fractional cross section, R(AA) is observed to be systematically larger in Cu + Cu collisions compared to Au + Au. However, for the same number of participating nucleons, R(AA) is essentially the same in both systems over the measured range of pT, in spite of the significantly different geometries of the Cu + Cu and Au + Au systems.

Recoil polarization for delta excitation in pion electroproduction

We measured angular distributions of recoil-polarization response functions for neutral pion electroproduction for W = 1.23 GeV at Q(2) = 1.0 (GeV/c)(2), obtaining 14 separated response functions plus 2 Rosenbluth combinations; of these, 12 have been observed for the first time. Dynamical models do not describe quantities governed by imaginary parts of interference products well, indicating the need for adjusting magnitudes and phases for nonresonant amplitudes. We performed a nearly model-independent multipole analysis and obtained values for Re (S(1+)/M(1+)) = -(6.84 +/- 0.15)% and Re (E(1+)/M(1+)) = -(2.91 +/- 0.19)% that are distinctly different from those from the traditional Legendre analysis based upon M1+ dominance and ll(pi) < or = 1 truncation.

Highly Effective and Recyclable Dendritic Ligands for the Enantioselective Aryl Transfer Reactions to Aldehydes

[reaction: see text] A series of chiral pyrrolidinylmethanol-based dendritic ligands were synthesized for application in enantioselective aryl transfer reactions to aldehydes with the (ArBO)3/ZnEt2 system in up to 98% ee.