Virtual and experimental high-throughput screening (HTS) in search of novel inosine 5′-monophosphate dehydrogenase II (IMPDH II) inhibitors

IMPDH (Inosine 5??-monophosphate dehydrogenase) catalyzes a rate-limiting step in the de novo biosynthesis of guanine nucleotides. IMPDH inhibition in sensitive cell types (e.g., lymphocytes) blocks proliferation (by blocking RNA and DNA synthesis as a result of decreased cellular levels of guanine nucleotides). This makes it an interesting target for cancer and autoimmune disorders. Currently available IMPDH inhibitors such as mycophenolic acid (MPA, uncompetitive inhibitor) and nucleoside analogs (e.g., ribavirin, competitive inhibitor after intracellular activation by phosphorylation) have unfavorable tolerability profiles which limit their use. Hence, the quest for novel IMPDH inhibitors continues. In the present study, a ligand-based virtual screening using IMPDH inhibitor pharmacophore models was performed on in-house compound collection. A total of 50,000 virtual hits were selected for primary screen using in vitro IMPDH II inhibition up to 10???M. The list of 2,500 hits (with >70?% inhibition) was further subjected to hit confirmation for the determination of IC₅₀ values. The hits obtained were further clustered using maximum common substructure based formalism resulting in 90 classes and 7 singletons. A thorough inspection of these yielded 7 interesting classes in terms of mini-SAR with IC₅₀ values ranging from 0.163???M to little over 25???M. The average ligand efficiency was found to be 0.3 for the best class. The classes thus discovered represent structurally novel chemotypes which can be taken up for further development.     

Stereoselective trans-reduktion tert. Propargylamine mit DIBAH zu (E)-Allylaminen

The reduction of tertiary propargylamines with DIBAH in toluene affords high yields of allylamines with trans-configuration exclusively.     

Menthatrienes and the Oxidation of Limonene

The oxidation of limonene with mercuric acetate gives a mixture containing mentha-1. 3. 8-triene, the hydrocarbon of parsley, and its isomer, mentha-1. 4. 8-triene. Selenium dioxide oxidation of limonene in alcohol gives as the main product mentha-1. 8-dien-4-ol, and pyrolysis of the acetate of the latter, or of mentha-1. 8-dien-10-yl acetate (the main product of the oxidation of limonene with selenium dioxide in acetic anhydride), also gives a mixture of menthatrienes. A discussion of the selenium dioxide oxidation of limonene is presented.     

Die Konzentration an freiem molekularem Jod in wäßrigen PVP-jodhaltigen Systemen und ihre Änderung mit der Temperatur

The concentration of free iodine and its variation in the temperature range 10–40°C has been determined by the potentiometric method in nine commercial PVP-iodine products as well as in pure aqueous solutions (1, 5 and 10%) of PVP-iodine of the type 17/12 and 90/04. In addition, aqueous solutions of PVP-iodine 30/06 of the same concentrations have been measured in the temperatur range 0–70°C. The commercial products showed a remarkably great spread in the concentration of free iodine (0.2–10 ppm at 25°C), which may be attributed to the different compositions, especially the ratio of total iodine to iodide as well as the kind and quantity of organic-pharmaceutical constituents. All tested PVP-iodine systems showed a significant—and unexpectedly similar—change of the concentration of free iodine by the temperature. The results concerning its relative alteration fit to an exponential function of the form $$\Delta \% [I_2 ]_{\Delta t} = 100[10^{(0.23 \pm 0.0026)\Delta t} 1]$$ which is valid from 10 to 40°C. Following this equation [I₂] increases about 5.4 resp. 100% if the temperature raises about 1.0 resp. 13.1°C. This increase of [I₂] must be considered in the application of PVP-iodine preparations as disinfectants or antiseptics at living tissues. Because of their higher temperature (c. 30–36°C) the applicated PVP-iodine preparations exhibit a significant higher [I₂] than at room temperature (Δt=10–16°C: Δ% [I₂]=70–130%). Therefore also a significant higher degerming efficiency can be expected compared toin vitro experiments, which are conducted in general at room temperature.     

Investigation on the corrosion of brazed joints by means of scanning auger microprobe

As a model experiment for the corrosion behaviour of brazed joints in water pipes made of stainless steel, some tens ofan broad joints made of three different brazes (Ag/Cu/In/Ni, Ag/Cu/Sn, Ag/Cu) were exposed to streaming water at different Cl^– concentrations. The samples were polarized. The three-dimensional distribution of the corrosion products, obtained by Auger mapping and depth profiling, supplied some information about the corrosion behaviour of the joints.