Agropine,a new amino acid derivative from crown gall tumours

Agropine, an unusual compound produced in plant tumours was shown by mass spectrometry and proton and carbon-13 nmr spectroscopy to be a bicyclic derivative of glutamic acid and a hexitol sugar.     

Meeting Reports: International Workshop on the Protein Circular Dichroism Data Bank

The International Workshop on the Protein Circular Dichroism Data Bank (PCDDB) was held on April 11–13, 2005, at Birkbeck College, University of London, UK, under the sponsorship of the UK Biotechnology and Biological Sciences Research Council. The meeting was chaired by Bonnie Ann Wallace, Professor in the Department of Crystallography at Birkbeck College. The workshop organizing committee consisted of Dr. Robert W. Janes, Queen Mary, University of London, and Dr. Lee Whitmore, also of Birkbeck College.

Participants included experts in both conventional circular dichroism (CD) spectroscopy and representatives from synchrotron radiation circular dichroism (SRCD) beamlines: Prof. J. Sutherland of the NSLS SRCD beamlines U9b and U11 and East Carolina University (USA);     

Deterministic global optimization in ab-initio quantum chemistry

A large number of problems in ab-initio quantum chemistry involve finding the global minimum of the total system energy. These problems are traditionally solved by numerical approaches equivalent to local optimization. While these approaches are relatively efficient, they do not provide guarantees of global optimality unless a starting point sufficiently close to the global minimum is known apriori. Due to the enormous amount of computational effort required to solve these problems, more mathematically rigorous alternatives have so far received very little attention. Taking the above issue into consideration, this paper explores the use of deterministic global optimization in the context of Hartree-Fock theory, an important mathematical model applied in many quantum chemistry methods. In particular, it presents a general purpose approach for generating linear relaxations for problems arising from Hartree-Fock theory. This was then implemented as an extension to the ${{\tt COUENNE}}$ (Convex Over and Under ENvelopes for Nonlinear Estimation) branch and bound mixed integer non-linear programs solver. Proof of concept calculations that simultaneously optimise the orbital coefficients and the location of the nuclei in closed-shell Hartree-Fock calculations are presented and discussed.     

C−C Bond Formation of Benzyl Alcohols and Alkynes Using a Catalytic Amount of KOtBu: Unusual Regioselectivity through a Radical Mechanism

We report a C?C bond‐forming reaction between benzyl alcohols and alkynes in the presence of a catalytic amount of KO^tBu to form α‐alkylated ketones in which the C=O group is located on the side derived from the alcohol. The reaction proceeds under thermal conditions (125 °C) and produces no waste, making the reaction highly atom efficient, environmentally benign, and sustainable. Based on our mechanistic investigations, we propose that the reaction proceeds through radical pathways.     

Quantitative Screening of Hydrolase Libraries Using pH Indicators: Identifying Active and Enantioselective Hydrolases

Rapid and quantitative screening in 96-well microplates can identify active and enantioselective hydrolases. Hydrolysis of esters releases a proton, which can be detected with pH indicators by colorimetry (figure). Using pure enantiomers, we measured the initial rates of enzyme-catalyzed hydrolysis. The relative initial rate approximates the enantioselectivity. This screening greatly speeds up selection of the best hydrolase for a synthesis.     

1‐{5‐[2‐(Tri­fluoro­methyl)­phenyl]‐1,3,4‐thia­diazol‐2‐yl}guanidinium chloride

In the title compound, C₁₀H₉F₃N₅S⁺·Cl^?, which was developed as a potential anticonvulsant, the phenyl ring, the thia­diazo­le ring and the guanidinium moiety are all planar. There is a dihedral angle of 48.9 (1)° between the thia­diazole and phenyl rings which prevents steric hindrance arising from the π bonds within the former, and the tri­fluoro­phenyl moiety attached to the latter. The thia­diazole and guanidinium moieties are twisted by 12.7 (2)° with respect to each other. An extensive network of hydrogen bonds, predominantly involving the chloride ion, maintains the crystal structure.     

Manganese Catalyzed Hydrogenation of Organic Carbonates to Methanol and Alcohols

The first example of a homogeneous catalyst based on an earth‐abundant metal for the hydrogenation of organic carbonates to methanol and alcohols is reported. Based on the mechanistic investigation, which indicates metal‐ligand cooperation between the manganese center and the N?H group of the pincer ligand, we propose that the hydrogenation of organic carbonates to methanol occurs via formate and aldehyde intermediates. The reaction offers an indirect route for the conversion of CO₂ to methanol, which coupled with the use of an earth abundant catalyst, makes the overall process environmentally benign and sustainable.     

Synthesis of a triphenylphosphine reagent on non-cross-linked polystyrene support: application to the Staudinger/Aza-wittig reaction

A new triphenylphosphine reagent linked to a linear polystyrene was synthesized. The reactivity of this phosphine-bound polymer is superior to that of the phosphine bound to cross-linked polystyrene. The polymer reacted very rapidly with azides to generate iminophosphoranes which could then react with aldehydes to generate imines in good yields and high purities.