Direct and highly regioselective and enantioselective allylation of β-diketones

The enantioselective allylation of ketones is a problem of fundamental importance in asymmetric reaction design, especially given that only a very small number of methods can generate tertiary carbinols. Despite the vast amount of attention that synthetic chemists have given to this problem, success has generally been limited to just a few simple ketone types. A method for the selective allylation of functionally complex ketones would greatly increase the utility of ketone allylation methods in the chemical synthesis of important targets. Here we describe the operationally simple, direct, regioselective and enantioselective allylation of β-diketones. The strong tendency of β-diketones to act as nucleophilic species was overcome by using their enol form to provide the necessary Br?nsted-acid activation. This reaction significantly expands the pool of enantiomerically enriched and functionally complex tertiary carbinols that may be easily accessed. It also overturns more than a century of received wisdom regarding the reactivity of β-diketones.     

Genome sequence of Bacillus cereus and comparative analysis with Bacillus anthracis

Bacillus cereus is an opportunistic pathogen causing food poisoning manifested by diarrhoeal or emetic syndromes. It is closely related to the animal and human pathogen Bacillus anthracis and the insect pathogen Bacillus thuringiensis, the former being used as a biological weapon and the latter as a pesticide. B. anthracis and B. thuringiensis are readily distinguished from B. cereus by the presence of plasmid-borne specific toxins (B. anthracis and B. thuringiensis) and capsule (B. anthracis). But phylogenetic studies based on the analysis of chromosomal genes bring controversial results, and it is unclear whether B. cereus, B. anthracis and B. thuringiensis are varieties of the same species or different species. Here we report the sequencing and analysis of the type strain B. cereus ATCC 14579. The complete genome sequence of B. cereus ATCC 14579 together with the gapped genome of B. anthracis A2012 enables us to perform comparative analysis, and hence to identify the genes that are conserved between B. cereus and B. anthracis, and the genes that are unique for each species. We use the former to clarify the phylogeny of the cereus group, and the latter to determine plasmid-independent species-specific markers.     

Carboxypeptidases from A to Z: implications in embryonic development and Wnt binding

Carboxypeptidases perform many diverse functions in the body. The well-studied pancreatic enzymes (carboxypeptidases A1, A2 and B) are involved in the digestion of food, whereas a related enzyme (mast-cell carboxypeptidase A) functions in the degradation of other proteins. Several members of the metallocarboxypeptidase gene family (carboxypeptidases D, E, M and N) are more selective enzymes and are thought to play a role in the processing of intercellular peptide messengers. Three other members of the metallocarboxypeptidase gene family do not appear to encode active enzymes; these members have been designated CPX-1, CPX-2 and AEBP1/ACLP. In this review, we focus on the recently discovered carboxypeptidase Z (CPZ). This enzyme removes C-terminal Arg residues from synthetic substrates, as do many of the other members of the gene family. However, CPZ differs from the other enzymes in that CPZ is enriched in the extracellular matrix and is broadly distributed during early embryogenesis. In addition to containing a metallocarboxypeptidase domain, CPZ also contains a Cys-rich domain that has homology to Wnt-binding proteins; Wnts are important signaling molecules during development. Although the exact function of CPZ is not yet known, it is likely that this protein plays a role in development by one of several possible mechanisms.     

The threshold for the smell of acetone and its relationship to the ability to taste phenylthiocarbamate

Zusammenfassung Individuelle Geruchsschwellenwerte für Azeton folgen einer trimodalen Kurve und stehen in Beziehung zur Fähigkeit, PTC zu schmecken. Diese Befunde deuten darauf hin, dass die Geruchsempfindlichkeitfür Azeton eine genetische Grundlage hat.

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Based on a report accepted by the Israel Ministry of Education in partial fulfillment of matriculation requirements ofLea Reznik, and constituting an extension of the work ofHenry Tabe.     

Electron-phonon coupling reflecting dynamic charge inhomogeneity in copper oxide superconductors

The attempt to understand copper oxide superconductors is complicated by the presence of multiple strong interactions in these systems. Many believe that antiferromagnetism is important for superconductivity, but there has been renewed interest in the possible role of electron-lattice coupling. The conventional superconductor MgB2 has a very strong electron-lattice coupling, involving a particular vibrational mode (phonon) that was predicted by standard theory and confirmed quantitatively by experiment. Here we present inelastic scattering measurements that show a similarly strong anomaly in the Cu-O bond-stretching phonon in the copper oxide superconductors La(2-x)Sr(x)CuO4 (with x = 0.07, 0.15). Conventional theory does not predict such behaviour. The anomaly is strongest in La(1.875)Ba(0.125)CuO4 and La(1.48)Nd(0.4)Sr(0.12)CuO4, compounds that exhibit spatially modulated charge and magnetic order, often called stripe order; it occurs at a wave vector corresponding to the charge order. These results suggest that this giant electron-phonon anomaly, which is absent in undoped and over-doped non-superconductors, is associated with charge inhomogeneity. It follows that electron-phonon coupling may be important to our understanding of superconductivity, although its contribution is likely to be indirect.