Evidence of an equilibrium between selenides and osmium(VIII) reagents and selenoxides and osmium(VI) reagents

Driving the equilibrium between selenides and osmium(VIII) reagents with selenoxides and osmium(VI) by a subsequent reaction (rearrangement of allyl selenoxides to allyl alcohols or addition of osmium(VIII) species on C=C double bonds) to one side, allows the transformation of methyl geranyl selenides to linalool and of methyl citronellyl selenoxide to 6,7-dihydroxy citronellyl selenide.     

Solid supported fluoronitroaryl triazenes as immobilized and convertible Sanger reagents--synthesis and SNAr reactions towards a novel preparation of 1-alkyl-5-nitro-1H-benzotriazoles

Synthesis of novel fluoronitroaryl triazenes in liquid phase and on solid support have been described; mild displacement of the fluoride ion with various nucleophiles provides access to substituted arenes which in turn can be cleaved to provide a unique access to 1-alkyl-5-nitro-1H-benzotriazole.     

Computer-aided design of chiral ligands. Part III. A novel ligand for asymmetric allylation designed using computational techniques

[reaction: see text] Computer-aided design protocols to identify new chiral ligands for reactions proceeding through well-defined transition states are outlined. Ligand families are discovered via computational screening of large structural databases such as the Cambridge Structural Database. Using this method, a novel cis-decalin ligand has been identified as a chiral auxiliary for the allylboration of aldehydes. Synthesis, resolution, and evaluation revealed that this new auxiliary provided the aldehyde facial approach upon which the design was predicated.     

A readily-accessible (+)-sparteine surrogate

A "(+)-sparteine-like" chiral diamine, readily synthesized in three steps from (-)-cytisine, has been evaluated in four different asymmetric transformations; in each case, selectivity in an enantiocomplementary fashion to (-)-sparteine was observed.     

Cosine modulated HSQC: a rapid determination of (3)J(HNHalpha) scalar couplings in (15)N-labeled proteins

A two-dimensional HSQC-based NMR method, (15)N-COSMO-HSQC, is presented for the rapid determination of homonuclear (3)J(HNHalpha) couplings in (15)N-labeled proteins in solution. Scalar couplings are extracted by comparing the intensity of two separate datasets recorded with and without decoupling of the (3)J(HNHalpha) during a preparation period. The scalar couplings are introduced through a cosine modulation of the peak intensities. The experiment relies on a BIRD sandwich to selectively invert all amide protons H(N) and is very simple to implement. (3)J(HNHalpha) couplings were determined using both the (15)N-COSMO-HSQC and quantitative-J on (15)N-labeled chemokine RANTES. The two experiments show well-correlated values.     

Maximal Convex Subgroups of the Automorphism Group of a Doubly Transitive Chain

We characterise all maximal convex l-subgroups of A(), the automorphismgroup of a doubly transitive chain of countable coterminality.We then determine, up to isomorphism, all doubly transitiveactions of the l-group A(). Finally, assuming the ContinuumHypothesis, we show that there exists an unbounded chain ofproper prime subgroups of A().     

Reversibly-formed ion pairs are not involved during the solvolysis of N,O-diacetyl-N-arylhydroxylamines

Appropriate oxygen-18 labeling experiments demonstrate that N,O-diarylhydroxylamines do not undergo solvolysis $\text{via}$ the reversible formation of ion pairs. This is in total conflict with the conclusions from previous indirect kinetic studies of these ultimate carcinogen models.     

Shearing of oriented polyethylene and polypropylene

To learn more about the out-of-plane deformation of polymer lamellae during drawing, we have measured the resistance to shear along various planes in uniaxially oriented polyethylene and polypropylene. Fissures parallel to the orientation axis in oriented materials always cause too small an experimental value for the resistance of crystal glide parallel to the chain axes, but a rough estimate for the resistance to crystal glide is obtained using the elastic anisotropy. Also, the results suggest that kinking can be easier than glide when glide is inhibited by tie molecules.