Highly diastereoselective allylic azide formation and isomerization. Synthesis of 3(2'-amino)-beta-lactams

The stereoselective anti SN2' attack of NaN3 to 3-alkenyl-3-bromo-azetidin-2-ones gave a mixture of diastereomeric azides in fast equilibrium. The [3,3]-sigmatropic rearrangement of allylic azides occurred with complete stereocontrol, allowing the equilibrium to be directed preferentially toward the (E)- or (Z)-isomer, useful precursors of 3(2'-amino)-beta-lactams. [reaction: see text]     

13C-NMR. Analysis of Dihydrogranaticin Methyl Ester. A case of mixed biogenesis

The ¹³C-NMR. spectrum of dihydrogranaticin methyl ester has been completely analyzed. Feeding experiments of CH₃ ¹³COONa to a culture of Streptomyces olivaceus have shown that only a sixteen carbon moiety of the antibiotic granaticin is of polyketide origin, thus confirming the hypothesis of a mixed biogenesis for this natural substance.     

A history of thermochemistry through the tribulations of its devotees

The history and the evolution of thermochemistry are covered in a number of excellent books. In order not to repeat what has already been written, this paper will be concerned with thermochemists as persons through their odd stories and anecdotes, of hot, enduring and even fierce debates, of accidents in the laboratory. This revised version was published online in July 2006 with corrections to the Cover Date.     

Classical trajectory study of the dissociation of hydrogen on copper single crystals: II. Cu(100) and Cu(110)

We report a second series of classical trajectory calculations for the activated dissociation of hydrogen on copper single crystals. We have modified the empirical interaction potential surface used previously by raising the energy requirements for dissociation, thereby lowering the dissociation probabilities and bringing their magnitudes in line with experiment. Dissociation probabilities on both a Cu(100) and Cu(110) surface for H₂ and D₂ are computed. The results, while in reasonable magnitude agreement with experiment, still do not fit the experimental translational energy dependence well and do not predict the correct isotope effect for Cu(110). A detailed comparison of the differences between the ground and first vibrationally excited states for the (100) and (110) surfaces suggest that within the approximations of this model calculation, the potential surfaces employed have underestimated the effects of surface roughness in determining the incident energy and angle dependence of the dissociation probabilities.     

Synthesis of oxazolidin-2-ones using carbonate ion on a polymeric support

Through the insertion of a carbon dioxide molecule, the oxazolidin-2-ones ($\text{5a}$) and ($\text{5b}$) were prepared by treataent of the salts ($\text{4a}$) and ($\text{4b}$) with carbonate anion on polymeric support. The hydrolysis under basic conditions of ($\text{5a}$) and ($\text{5b}$) afforded the erythro-3-amino-1,2-diols ($\text{6a}$) and ($\text{6b}$) which were fully acetylated: the 2-amino-2-deoxyerythritol derivative ($\text{7b}$) was obtained in 91% yield.     

Synthesis and biological evaluation of azido- and aziridino-hydroxyl-beta-lactams through stereo- and regioselective epoxide ring opening

Two new classes of azido- and aziridino-hydroxyl-beta-lactam containing structures have been prepared by means of a stereo- and regioselective epoxide ring opening. The straightforwardness of the procedure makes this strategy useful for the synthesis of potentially bioactive compounds. Some selected examples showed promising activity in acyl CoA-cholesterol acyltransferase inhibition assays.     

Working group report: Heavy-ion physics and quark-gluon plasma

This is the report of Heavy Ion Physics and Quark-Gluon Plasma at WHEPP-09 which was part of Working Group-4. Discussion and work on some aspects of quark-gluon plasma believed to have created in heavy-ion collisions and in early Universe are reported.