Regioselective Hydrolysis of Cocaine and A Convenient Acylation Procedure by Benzoylecgonine

Regioselective hydrolysis of cocaine led, according to the reaction conditions, either to benzoylecgonine or to ecgonine methyl ester. Acylation with benzoylecgonine was readily achieved when benzotriazolyloxytrisdimethylamino-phosphonium (BOP) was used as a coupling agent.     

Enzymatic oxidation of para-substituted arenes: access to new non-racemic chiral metabolites for synthesis

A series of para-substituted benzene derivatives were subjected to whole-cell fermentation with Escherichia coli JM109 (pDTG601), an organism expressing toluene dioxygenase (TDO). Several compounds proved to be excellent substrates for TDO, including 4-bromo-phenylacetylene, 4-bromobenzaldehyde, 4-bromobenzyl alcohol and 4-bromo-allylbenzene. Some of the first para-functionalized diene diols produced using TDO, are useful substrates for further synthetic manipulations, including their use in the potential synthesis of complex natural products.     

Alkyloxycarbonyl group migration in furanosides

A migration of methyloxycarbonyl group from secondary to primary hydroxyl was observed in furanosides (ribosides and xylosides) under usual desilylation conditions using tetrabutylammonium fluoride. The migration was studied further on several alkyloxycarbonyl furanosides under either basic or acidic conditions. As follows from ¹³C labelling experiments and product distribution, the migration in xylosides, proceeds intramolecularly via six-membered cyclic carbonate, whereas in ribosides, the migration is intermolecular. Acidic conditions prevented the migration in ribosides whereas the migration in xylosides was circumvented under neutral conditions.     

Characterisation of human hair surfaces by means of static ToF-SIMS: A comparison between Ga and C60 primary ions

This study deals with the secondary ion yield improvement induced by using C₆₀⁺ primary ions instead of Ga⁺ ones to characterize human hair surfaces by ToF-SIMS. For that purpose, a bunch of hair fibres has been analysed with both ion sources. A high improvement is observed for the detection of amino acids with C₆₀⁺ primary ions as compared to Ga⁺ ions. As an example, a yield enhancement factor greater than 3000 is found for the CNO⁻ peak. A similar gain is observed for the positive secondary ions characteristic of the amino acids. Most of the atomic ions, such as Ca⁺, O⁻ and S⁻, constitute minor peaks with C₆₀⁺ ions while they often dominate the spectrum in the case of Ga⁺ ions. However, with the C₆₀⁺ source, a series of inorganic combination peaks with the elements Ca, S and O are observed in the positive spectra (i.e. HCaSO₄⁺), while they are marginal with the Ga⁺ source. For the mass range beyond 100 m/z and in both polarities, the hair fingerprints are similar with both sources. In average, for a comparable number of primary ions per spectrum, the C₆₀⁺ ion source gives intensities between two and three orders of magnitude higher than the Ga⁺ one.     

Nucleic acid-metal interactions. IV. Complexes of Ag(I) with thymine and cytosine from studies of UV and IR dichroic spectra

The linear dichroism of the complexes of thymine and cytosine with silver(I) ions dispersed in stretched polyvinylalcohol films was measured in the infrared and in the near ultraviolet regions of the spectrum. The infrared results were helpful in establishing the orientation of the complexes in the films; they also confirmed that the site of silver binding in the case of cytosine involves the carbonyl oxygen. The ultraviolet spectra were deconvoluted into separate electronic transitions and the corresponding transition moments of silver complexes were determined.     

Efficient polynomial reduction

H-bases are bases for polynomial ideals, characterized by the fact that their homogeneous leading terms are a basis for the associated homogeneous ideal. In the computation ofH-bases without term orders, an important task is to determine the orthogonal projection of a homogeneous polynomial to certain subspaces of homogeneous polynomials with respect to a given inner product. One way of doing so is to use an orthogonal basis of the subspace. In this paper, we present and study a method to efficiently compute such a basis for a particular but important inner product.     

Distribution of the inter and intra inertia in conditional MCA

Conditional Multiple Correspondence Analysis (MCA), where a control variable plays the role of a partition model, allows us to decompose global inertia into between inertia and within inertia. The problem is to assess when the conditioning variable gives different results with respect to the unconditional analysis. In this paper, we study the asymptotic distribution function of these inertias, which can allow us to determine whether conditioning is significant. Some simulations were performed to corroborate the established results.