Structural analogues of the bimetallic reaction center in acetyl CoA synthase: a Ni--Ni model with bound CO

Models for the active site of the acetyl CoA synthase (ACS) were synthesized by attachment of Cu+ and Ni(0) to nickel diaminodithiolate (S2N2) and diamidodithiolate (S2N2') complexes. The Ni-Ni species form stable CO adducts, i.e., [{(CO)2Ni}{NiS2N2'}]2-, whereas the Cu-NiS2N2 and Cu-NiS2N2' models do not. These results provide supporting evidence for a biological role for reduced nickel in ACS.     

1H and 13C spectral assignment of 2(1H)-pyridone derivatives

1H and 13C NMR spectroscopic data for 4-aryl-3,4-dihydro-6-methyl-2(1H)pyridone derivatives were fully assigned by a combination of one- and two- dimensional experiments (DEPT, HMBC, HMQC, COSY, NOE).     

Novel hexahydrofuro[3,4-b]-2(1H)-pyridones from 4-aryl substituted 5-alkoxycarbonyl-6-methyl-3,4-dihydropyridones

The title compounds 6 have been prepared in a one-step procedure from the corresponding 4-aryl substituted 5-alkoxycarbonyl-6-methyl-3,4-dihydropyridones 4 in good yields. Quantum chemical calculations reveal a non-planar molecule with a distorted dihydropyridone ring and two favoured conformations. The 13C nmr data and theoretical calculations support a strong push-pull effect on the olefinic moiety.     

Synthesis of all low-energy stereoisomers of the tris(pyrrolidinoindoline) alkaloid hodgkinsine and preliminary assessment of their antinociceptive activity

The previously unknown stereoisomers 3, 4, ent-1, and ent-4 of the tris(pyrrolidinoindoline) alkaloids hodgkinsine (1) and hodgkinsine B (2) were prepared by stereocontrolled total synthesis. In each synthesis, a catalyst-controlled intramolecular Heck reaction was the key step in appending a third cis-pyrrolidinoindoline ring to a hexacyclic chimonanthine precursor. Results of the preliminary evaluation of these hodgkinsine stereoisomers in the tail flick and capsaicin pain models are reported.     

Experimental and theoretical structural study of 2‐pyridyl‐ and 4‐hydroxyphenyl‐1,4‐dihydropyridine derivatives

A series of substituted 1,4‐dihydropyridines (1,4‐DHPs) has been synthesised following the well‐known Hantzsch's procedure for symmetrical 1,4‐DHP. The structures of these compounds have been thoroughly studied by X‐ray crystallographic analysis and semiempirical (AMI) calculations. A good agreement is found between the theoretical and experimental results. In all cases, the most stable conformation fulfils all the requirements needed for exhibiting an antagonist calcium effect.     

The production ofJ/ψ in 200 GeV/A oxygen-uranium interactions

The dimuon production in 200 GeV/nucleon oxygen-uranium interactions is studied by the NA 38 Collaboration. The production ofJ/ψ, correlated with the transverse energyET, is investigated and compared to the continuum, as a function of the dimuon massM and transverse momentumPT. A value of 0.64±0.06 is found for the ratio (ψ/Continuum at highET)/(ψ/Continuum at lowET), from which theJ/ψ relative suppression can be extracted. This suppression is enhanced at lowPT.