Stereoselective synthetic approaches to highly substituted cyclopentanes via electrophilic additions to mono-, di-, and trisubstituted cyclopentenes

Electrophilic additions to allylically substituted alkenes are of broad synthetic utility. The control of stereoselectivity in such reactions has attracted considerable interest. However, the effect of allylic and homoallylic substituents in cyclopentenyl systems has not been investigated systematically. Studies on a series of mono, di-, and trisubstituted cyclopentenes are reported in which trans-vicinal-additions favor a syn-selective approach of electrophiles to the cyclopentene system. The formal addition of HOBr, HOCl, CH(3)SCl, and dimethyl(methylthio)sulfonium tetrafluoroborate (DMTSF)/NaN(3) with a variety of cyclopentene substrates has been carried out, and the effects of various allylic substituents on these selectivities have been examined. Additions of HOBr, HOCl, and DMTSF to highly functionalized substrates proceed predictably with syn selectivity, giving predominantly or exclusively one product. Methanesulfenyl chloride additions are less predictable, but can be tuned by suitable alteration of solvent and substrate. Results have proven useful in total syntheses of (+)-trehazolin and (+)-allosamidin.     

Calculation of electrophoretic mobilities in water-organic modifier mixtures in capillary electrophoresis

In order to correlate/predict electrophoretic mobility data in the mixture of water+organic modifier four equations have been presented and examined. The experimental mobilities of five analytes were determined in a water-methanol mixture. These data have been used to assess the accuracy and predictability of the models. Also, some previously published mobility data in water-organic modifier mixtures has been employed for further evaluation of the models. The models produced accurate results and the means of percentage deviations were in the range of 0.66-1.30.     

Polymenthylenebiphenyl polyanions by metallation—elimination

The 3,3′,5,5′-tetramethylenebiphenyl tetraanion, prepared in good yield by metallation-elimination, gives tetrasubstituted biphenyl derivatives, e.g., with H₂O, D₂O, methyl iodide, and trimethylsilyl chloride. The reaction sequence, starting from alkylated cyclohexanones, provides a general synthetic route to symmetrical polysubstituted biphenyls.     

Spalling in liquids

A new mechanism for exciting cavitation has been identified. Surface-reflected shock waves can produced localized spalling in liquids. This spalling mechanism forms cavities which then collapse under the influence of gravity and atmospheric pressure. The form of the closure pulses generated by cavity collapse characterizes this new type of cavitation.     

Stability of nuclear matter against neutral pion condensation

The global stability of the uniform ground state of nuclear matter is tested relative to a π⁰-condensed state characterized by static spin-(isospin-) waves. Strong nuclear correlations are introduced into the trial wave functions for each phase, thereby permitting models of the realistic two-nucleon force to be employed. In low cluster-order comparison, the uniform phases of symmetrical nuclear matter and neutron matter are emphatically favored over the entire density range considered.     

The hyperfine structure and hyperfine anomaly of 161Dy and 163Dy

The hyperfine structure of ¹⁶¹Dy and ¹⁶³Dy for five transitions hasbeen measured with a tunable dye laser and a thermal velocity atomic beam. Values for the magnetic dipole and electric quadrupole coupling constants have been determined for the relevant excited states. The hyperfine anomaly parameters, Δ, which are extracted are interpreted in terms of available atomic wave functions.     

Molecular-orbital X-rays from 1 GeV 208Pb + 208Pb and 209Bi + 209Bi collisions

We have measured the spectra of continuum X-rays above the characteristic K lines for 4.5 to 4.8 MeV/N ²⁰⁸₈₂Pb → ²⁰⁸₈₂Pb, Pb → Bi, Bi → Pb and Bi → Bi collisions. Above ≈400 keV X-ray energy the spectral shape and intensity agree roughly with calculations of Kirsch et al. for the 1sσ molecular-orbital (MO) X-ray spectrum from Pb-Pb. Deviations from the theory below ≈400 keV suggest transitions to other MO's.     

Total synthesis of slow reacting substances (SRS). “Leukotriene C-2” (11-trans-leukotriene C) (3) and leukotriene D (4)

Syntheses are described for the “slow reacting substances” 11-$\text{trans}$-leukotriene C (3) (previously known as leukotriene C-2) and leukotriene D (4), the cys-gly analog of leukotriene C (2). The synthesized leukotrienes 3 and 4 were instrumental in the assignment of structure to these members of the family of naturally occuring slow reacting substances which includes also 2.     

Applications of ESCA to polymer chemistry. III. Structures and bonding in homopolymers of ethylene and the fluoroethylenes and determination of the compositions of fluoro copolymers

Molecular core binding energies have been measured by ESCA for the homopolymers of ethylene and the fluoroethylenes. The data are interpreted in terms of semiempirical all-valence electron SCF MO calculations in the CNDO/2 formalism, in conjunction with the charge potential model. The results are used as a basis for interpreting the measured core binding energies of some Viton and Kel F type polymers. The routine application of ESCA to the determination of copolymer compositions is described.     

Application of the method of correlated basis functions to nuclear matter

The binding energy of nuclear matter is evaluated for Hamada-Johnston and other potentials in terms of non-central correlations determined by constrained variation. The ground-state energy expectation value is computed through three-body cluster order, and the effects of residual correlations incorporated approximately using non-orthogonal perturbation theory.