Bis((2-methoxymethyl)pyrrolidine)phosphine as effective chiral auxiliary for the stereoselective synthesis of chiral ferrocenyl diphosphines

The bis(2-methoxymethyl pyrrolidine)phosphine moiety is shown to be a very effective chiral auxiliary for the ortho- and diastereoselective lithiation of ferrocene, thereby allowing the highly selective attachment of various electrophiles to the cyclopentadienyl ring of ferrocene. The potential of the methodology is demonstrated by the synthesis of Kephos, a new family of ferrocenyl diphosphines and of OH-Taniaphos derivatives.     

New Applications of the CD Exciton Chirality Method. Stereochemical Assignment of Organic Compounds Containing Carboxylic Acid Groups

CD exciton chirality methods are described for the stereochemical assignment of organic compounds containing carboxylic acid groups. Using the chromophoric combination 2-naphthoate or 2-anthroate and 9-anthrylmethyl group the absolute stereochemistry of - and -hydroxy carboxylic acids can be deduced from a single CD measurement. Furthermore, as demonstrated with cyclic and acylic dicarboxylic acids, the direct esterification of sterically hindered carboxyl groups with 2-naphthol also allows the stereochemical assignment via CD spectroscopy.     

Alkoxide bridged Copper(II) Hinokitiolato and Tropolonato Complexes: Polymorphism,Reconstructive Phase Transition,and Magnetic Properties

Polymorphism and an unexpected reconstructive phase transition in [Cu(trop)(μ‐OMe)]₂ (trop = tropolonate) were studied by single crystal and powder X‐ray diffraction; the phase transition is associated with a huge hysteresis of ca. 200 °C. In the readily reproducible crystal form, the methoxide‐bridged dinuclear subunits aggregate to infinite chains by longer bonds in the Jahn‐Teller distorted coordination sphere. Analogous alkoxide‐bridged derivatives with the substituted ligand hinokitiol (hino), [Cu(hino)(μ‐OR)]₂ (R = Me, Et, iPr) form pairs of dinuclear complexes and aggregate to discrete tetranuclear molecules. The inter‐cation distance patterns are reflected in the magnetic properties of these two structure types: Strong antiferromagnetic coupling within the dinuclear subunits is observed in either case, but susceptibility measurements confirm differences in exchange coupling between neighboring central Cu^II atoms.     

Samarium diiodide-induced couplings of carbonyl compounds with methoxyallene leading to 4-hydroxy 1-enol ethers

A surprising samarium diiodide-induced coupling reaction of carbonyl compounds with methoxyallene provided 4-hydroxy 1-enol ethers, which are versatile synthetic building blocks. In this coupling reaction, methoxyallene serves as an acrolein equivalent, which cannot directly be employed. [reaction: see text]     

Enantioselective catalysis in fine chemicals production

The application of enantioselective catalysis to the fine chemicals industry has great potential both from economic and ecological points of view, but to date has not been widely implemented on a technical scale. The author hopes that the award of the 2001 Chemistry Nobel Prize in this field will give the necessary impetus to future applications.     

Highly efficient proteinase assay with chromogenic substrates and its application in a study of enzyme inhibitors

A simple and rapid method for the determination of enzyme activities with chromogenic substrates is described. Trypsin and papain were used as model proteinases and N-benzoyl-dl-arginine p-nitroanilide (BAPNA) was applied as substrate. The enzyme assay was performed on a multi-scale using 96-well microtitration plates and product release was detected with the aid of an automatic plate reader, widely used in ELISA tests. The procedure was used for electrophoretic studies of trypsin and a crude papain preparation. It was also applied for the investigation of N-peptidyl-O-acylhydroxylamine proteinase inhibitors. In comparison with commonly used procedures with chromogenic substrates, the proposed approach consumes markedly reduced amounts of all reagents. It allows an almost unlimited number of samples to be assayed in a short time and should be applicable to the detection and determination of any enzyme activitiy where chromogenic substrates are applicable.