Cellular infection by HIV-1 is initiated with a binding event between the viral envelope glycoprotein gp120 and the cellular receptor protein CD4. The CD4–gp120 interface is dominated by two hotspots: a hydrophobic gp120 cavity capped by Phe43CD4 and an electrostatic interaction between residues Arg59CD4 and Asp368gp120. The CD4 mimetic small-molecule NBD-556 (1) binds within the gp120 cavity; however, 1 and related congeners demonstrate limited viral neutralization breadth. Herein, we report the design, synthesis, characterization, and X-ray structures of gp120 in complex with small molecules that simultaneously engage both binding hotspots. The compounds specifically inhibit viral infection of 42 tier 2 clades B and C viruses and are shown to be antagonists of entry into CD4-negative cells. Dual hotspot design thus provides both a means to enhance neutralization potency of HIV-1 entry inhibitors and a novel structural paradigm for inhibiting the CD4–gp120 protein–protein interaction.

Collisions of 11 Li 1 p at 68A MeV have been studied by correlational measurements. An excited state of 11 Li at E ‫ء‬ Ӎ 1.3 MeV was observed. The measured angular distributions show the dipole nature of the excitation of the 1.3-MeV peak. The structure of the excited states and the ground state of 11 Li is discussed. [S0031-9007(97)

Treatment of 1-alkenes with dimethylphenylsilylmethylmagnesium chloride in the presence of a cobalt-NHC complex in dioxane at 50 degrees C or higher provides the corresponding (E)-2-alkenes selectively. The isomerization is applicable to the stereoselective synthesis of (E)-crotylsilanes and (E)-1-propenylsilanes from the corresponding homoallylsilanes and allylsilanes, respectively.

Photoelectron spectra and solution UV absorption and magnetic circular dichroism (MCD) of hexamethyldisilane (1), hexaethyldisilane (2), hexa-tert-butyldisilane (3), and the 1,(n+2)-disila[n.n.n]propellanes [n = 4 (4) and 5 (5)] were measured, as was the linear dichroism (LD) of 3 and 4 partially aligned in stretched polyethylene. The results support the assignment of the lowest energy electronic absorption band of the disilanes 1−5 to a doubly degenerate σSiSi(HOMO) → π*SiC(LUMO) transition and of the next band, observed in the solution spectra of 2−4 and in the gas-phase spectrum of 1, to a σSiSi → σ*SiSi transition. MP2/VTZ optimized geometries of 1−5 and ab initio molecular orbital energies (HF/VTZ//MP2/VTZ) and ionization potentials (ROVGF/VTZ//MP2/VTZ) of these disilanes reproduce the reported geometries and the trends observed in the photoelectron spectra, respectively. B3LYP/6-31G(d,p) calculations of the Kohn−Sham orbital energies and TD B3LYP/6-31G(d,p) calculations of transition energies and intensities of 1 as a function of Si−Si bond length suggest that many of the features of the UV absorption spectrum of 3, including the small energy difference between the two transitions observed and the large extinction coefficient of the band peaking at higher energy (σSiSi → σ*SiSi), are due to its very long Si−Si bond.

Linearly-condensed polythiophenes (4 and 5) have been prepared and their characteristic aggregation behaviour as hydrogen-poor n: compounds in the solid state has been investigated in comparison with those of the lower homologues (2 and 3); the photoelectron spectra of the series 2-5 were measured in the solid state as well as in the gas phase. For 4 the difference in the ionization energies for the gaseous (adiabatic; 7.22 eV) and solid (threshold; 4.86 eV) states is significant, giving rise to a large polarization energy (2.36 eV), which is larger than the calculated value (1.83 eV) based on the packing density and molecular polarizability. This has been interpreted in terms of the intermolecular orbital interactions in the solid state of 4. Such an interaction has not been observed in the lower homologues (2 and 3).The discovery of an organic superconductor under ambient pressure from bis(ethy1enedithio)tetrathiafulvalene complexes (BEDT-TTF),13 ' has demonstrated that an enhancement in the spatial arrangements of intermolecular interactions is important in stabilizing the metallic states and, further, in designing organic superconductors.' Four sulfur atoms in the BEDT-TTF molecule, when introduced into the TTF skeleton, reinforce the interaction between quasi-one-dimensional stacks of BEDT-TTF molecules in the crystal through their side-byside packing arrangements.Against this background, we have investigated the linearlycondensed polythiophene 1. This polymer molecule bears essentially no hydrogen atoms in the molecular periphery, and is therefore expected to interact efficiently intermolecularly through S ---S contacts. Polycondensed thiophene itself has not yet been obtained. In contrast, lower homologues of a series of linearly-condensed thiophenes, i.e. thieno [3,2-b] thiophene(2) and thieno[3,2-b]thieno[2',3'-d]thiophene(3), which are regarded as the prototype of linearly-condensed polythiophenes, are already known. We have also prepared two higher homologues of this series; thieno [2",3": 4',5']thieno[2',3'-d]thieno[3,2-b]thiophene (4) and dithieno[2,3-d : 2',3'-d']thieno-[3,2-b: 4,5-br]dithiophene (9, which are isoelectronic with 1 2 3 4 5 Paper 2/00173J

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Photoelectron spectra were measured in the region between 6 and 21 eV for aniline, N,N-dimethylaniline, phenol, anisole, benzonitrile, acetophenone, nitrobenzene, and their methyl derivatives. The observed spectra were interpreted in terms of their MO’s obtained by the CNDO/2 and EHMO methods, the methyl-substituent effect and the steric hindrance effect being considered. Both effects are essential for the reliable assignment of the observed photoelectron spectra. We found a general tendency that the interaction of the doubly degenerate highest occupied orbitals (e1g) of the benzene ring with the highest occupied orbital of a substituent group is important for the interpretation of the observed lower energy (7∼12 eV) bands. The only exceptional case is the nitrobenzenes in which the lowest vacant orbital of the substituent group is rather close to the highest occupied orbitals of the benzene ring and the interaction between them is important. The effects of the substituent groups upon the observed photoelectron spectra are classified into four types.

Summary. The bands with I, < 13 eV in the photoclcctron spsctra of quinoline (IX), isoquinoline (X), cinnoline (XI), quinazoline (XII), and quinoxaline (XIII) h a w been reassigned in a way consistent with the assignment proposed for pyridine (11). the diazines (