Syntheses of puromycin from adenosine and 7-deazapuromycin from tubercidin, and biological comparisons of the 7-aza/deaza pair.

Protection (O5') of 2',3'-anhydroadenosine with tert-butyldiphenylsilyl chloride and epoxide opening with dimethylboron bromide gave the 3'-bromo-3'-deoxy xylo isomer which was treated with benzylisocyanate to give the 2'-O-(N-benzylcarbamoyl) derivative. Ring closure gave the oxazolidinone, and successive deprotection concluded an efficient route to 3'-amino-3'-deoxyadenosine. Analogous treatment of the antibiotic tubercidin [7-deazaadenosine; 4-amino-7-(beta-D-ribofuranosyl)pyrrolo[2,3-d]pyrimidine] gave 3'-amino-3'-deoxytubercidin. Trifluoroacetylation of the 3'-amino function, elaboration of the heterocyclic amino group into a (1,2,4-triazol-4-yl) ring with N,N'-bis[(dimethylamino)methylene]hydrazine, and nucleophilic aromatic substitution with dimethylamine gave puromycin aminonucleoside [9-(3-amino-3-deoxy-beta-D-ribofuranosyl)-6-(dimethylamino)purine] and its 7-deaza analogue. Aminoacylation [BOC-(4-methoxy-L-phenylalanine)] and deprotection gave puromycin and 7-deazapuromycin. Most reactions gave high yields at or below ambient temperature. Equivalent inhibition of protein biosynthesis in a rabbit reticulocyte system and parallel growth inhibition of several bacteria were observed with the 7-aza/deaza pair. Replacement of N7 in the purine ring of puromycin by "CH" has no apparent effect on biological activity.     

Die Bestimmung des l?slichen Quecksilberchlorides

Ohne Zusammenfassung     

Stationarity of multivariate particle systems

A particle system is a family of i.i.d. stochastic processes with values translated by Poisson points. We obtain conditions that ensure the stationarity in time of the particle system in R^d${\mathbb{R}}^d$ and in some cases provide a full characterisation of the stationarity property. In particular, a full characterisation of stationary multivariate Brown–Resnick processes is given.     

Flash Chemistry Extensively Optimized: High‐Temperature Swern–Moffatt Oxidation in an Automated Microreactor Platform

The generally accepted benefits of small lateral dimensions of microreactors (1 μm to 1 mm) enable a different way of performing synthetic chemistry: Extremely short contact times in the millisecond range can circumvent the need for performing highly exothermic and fast reactions at very low temperatures. In order to fully exploit this technology, such fast processes need to be redesigned and investigated for optimal reaction conditions, which can differ drastically from the ones traditionally applied. In a comprehensive study, we optimized the selective Swern–Moffatt oxidation of benzyl alcohol to benzaldehyde by varying five experimental parameters, including reaction time and temperature. Employing an ultrashort mixing and reaction time of only 32 ms, the optimal temperature was determined to be 70 °C, approximately 150 °C higher than in the conventional batch conditions. This remarkable difference shows both the potency of continuous‐flow chemistry as well as the urgency of a paradigm shift in reaction design for continuous‐flow conditions.     

Magnetoconductivity tensor analysis of anomalous transport effects in neutron irradiated HgCdTe epilayers

Hg_1−xCd_xTe(x0.22) samples grown by LPE on CdZnTe(111B)-oriented substrates were exposed to various doses of thermal neutrons (1.0×10¹⁶−1.7×10¹⁶ n/cm²) and subsequently annealed for 24 h in Hg overpressure to remove damage and reduce the presence of Hg vacancies. Extensive magnetotransport measurements were performed on these samples as part of an investigation into the use of elemental transmutation for efficient p-type doping of this material. The data were analyzed using a multi-carrier approach which incorporates various scattering mechanisms and the presence of two conduction channels of differing alloy content to describe the changes in the transport properties due to neutron irradiation.