Photoproduction of ϱ′(1.2) and ϱ′(1.6) in the final states π+ π− π+ π− and π+ π− π0 π0

The elastic photoproduction of four pions has been studied at incident photon energies between 2.8 and 4.8 GeV. Production cross-sections are presented and an analysis of the angular decay correlations is also described, indicating a large 1^? contribution in both final states, π⁺ π^? π⁺ π^? and π⁺ π^? π⁰ π⁰. A quantitative understanding of these and other available 4π photoproduction data in terms of the ρ′(～1.2GeV) and the ρ′(～1.6) is presented.     

Fibrewise completion and unstable Adams spectral sequences

We describe a tower of spaces whose inverse limit is a “fiberwise completion” of a fibrationE →B, and study the resulting spectral sequence converging to the homotopy groups of the space of lifts of a mapX →B. This is used to give a proof of the “generalized Sullivan conjecture”. All three authors were supported in part by the National Science Foundation.     

Low-Temperature X-ray Crystal-Structure Analysis of the Thermally Unstable Lithiated 2-Butenyl tert-Butyl Sulfide: A comparison with model ab initio MO calculations

Single crystals of the N,N,N′,N′-tetramethylethylenediamine (TMEDA) complex 6 of the title compound have been isolated. Compound 6 decomposes in the crystalline state above ?20°. From the bond lengths and angles obtained by X-ray crystal-structure analysis (data collected at ?70°), compound 6 is best described as a (E)-1-(tert-butylthio)-1-lithio-2-butene with the double bond acting as an additional ligand on lithium (unsymmetrical allylic group). The S-atom is in a cisoid arrangement in a common plane with the four C-atoms of the butenyl system. The t-Bu group and the Li-atom are located above and below this plane. The structure is discussed with respect to the reactivity of 6 (α/γ reactivity). The gross structure is reproduced surprisingly well by an ab initio SCF MO calculation of the model lithiopropene-1-thiol 7 (HS instead of t-BuS, CH₂ instead of CHCH₃, no solvation of Li). The prominent difference is the symmetry of the allyllic moiety in the calculated structure.     

The diastereospecific aprotic conjugate addition reactions of carbanions derived from allylic sulfoxides and allylic phosphine oxides.

The title carbanions undergo conjugate addition to cyclic enones in THF to deliver vinylic sulfoxides and vinylic phosphine oxides as single diastereomers.     

Inclusive π0 photoproduction and the quark-parton model

We present measurements on the inclusive structure function for π⁰ photoproduction for the incident photon energy range of 2.8–4.8 GeV. Comparisons are made with electroproduction data and it is found that the scaling behaviour already observed for finite q² continues to be valid at q² = 0.     

Carbon nucleophilic displacements on kamiya's azetidinone disulfide: Synthesis of c-2 modified penicillins

Novel carbon nucleophilic displacement reactions on Kamiya's azetidinone disulfide $\text{2}$ and the synthesis of the C-2 modified penams $\text{25}$, $\text{26}$ and $\text{27}$ from the intermediates $\text{8}$, $\text{9}$, and $\text{11}$ are described.     

Mesoscopic dynamic Monte Carlo simulations of the adsorption of proteinlike HP chains within laterally constricted spaces

Two-dimensional dynamic Monte Carlo simulations are applied to the protein-like HP chain model to investigate the influence of lateral confinement of the adsorbed chain on adsorption thermodynamics and the ensemble of accessible chain conformations. The structure of the model makes it possible to enumerate all possible chain conformations and thereby define with precision the relation between adsorption thermodynamics and changes in accessible chain conformations resulting from the adsorption process. Lateral confinement of the adsorbed chain is shown to dramatically reduce the number of accessible energy states and unique chain conformations such that, under certain conditions, adsorption is predicted to actually stabilize the chain against denaturation. Lateral confinement preferentially eliminates expanded conformations of the adsorbed chain, shifting the equilibrium from the unfolded state toward the native state. As a result, the conformational entropy of the adsorbed chain is predicted to be lower than that of the chain free in solution. The protein-like HP chain responds to an increase in the hydrophobicity of the sorbent surface by strongly favoring those conformations that minimize the overall internal energy of the system. As a result, adsorption severely destabilizes the native-state conformation. The ability of our simulation results to provide insights into underlying mechanisms for nonspecific protein adsorption is illustrated through qualitative comparison with activity data for hen egg-white lysozyme adsorbed on silica at different surface concentrations.     

Highly enantioselective phenyl transfer to aryl aldehydes catalyzed by easily accessible chiral tertiary aminonaphthol

A new chiral tertiary aminonaphthol ligand 3b served as a highly efficient ligand for the asymmetric catalytic phenyl transfer to aromatic aldehydes and a variety of chiral diarylmethanols was prepared in high ee values (ee up to 99%) and chemical yields. The straightforward syntheses of both 3b and its enantiomer provide an excellent opportunity for large-scale applications.     

The preparation and reactions of dienol ester and dienol ester derivatives of hagemann's ester and its t-butyl analogue

The efficient conversion of Hagemann's ester and its t-butyl analogue into dienol ethers and dienol esters, and reactions of the derived dienolates with electrophiles is described.     

The diastereospecific aprotic conjugate addition reactions of allylic anions-mechanistic aspects.

A ten-membered cyclic “chair-chair” - or “$\text{trans}$-decalyl”-like TS is proposed to account for the diastereospecific aprotic conjugate addition reactions of allylic carbanions bearing polar, charge-stabilizing groups.