Phenolic Components of Empetrum nigrum Extract and the Crystal Structure of One of Them

Four phenolic components are isolated from the CHCl ₃ extract ofEmpetrum nigrumL. Three of them are known from this plant. The fourth (6,8-dimethylpinocembrine) is isolated from crowberry for the first time. The previously proposed structure for 2'-methoxy-4'-hydroxy- ,-dihydrochalcone is confirmed by x-ray structure analysis     

Study of the effect of the nature of the side chain in esters of α-amino acids on the diastereoselectivity of condensation with 5(4H)-oxazolone in the synthesis of dipeptides with N-terminal N-acetylphenylalanine

Conditions for fast racemization of 5(4H)-oxazolones prepared from N-acylphenylalanine were found. Reactions of 4-benzyl-2-methyl-5(4H)-oxazolone with amino acid esters proceed diastereoselectively to give predominantly dipeptides comprising R-phenylalanine. The diastereoselectivity increases with complication of the structure of the side chain in the amino acid esters.     

Efficient Procedure for Preparing Salicyl Alcohols

A new convenient procedure was developed for selective ortho-hydroxymethylation of phenols by reaction of paraformaldehyde with a mixture of phenol and orthoboric acid. The method is general for phenols containing no strong electron-withdrawing substituents; it allows preparation of o-hydroxybenzyl alcohols of high purity in a high yield.     

Reductive Transformations of Organofluorine Compounds: III. Hydrodefluorination of Perfluoroalkylbenzenes Effected by Zn(Cu). The Unusual Behavior of Compounds Containing Perfluorinated tert-Butyl Group

Perfluoroalkylbenzenes under a treatment of a system Zn(Cu)-DMF-H₂O-electrolyte give rise in high yield to products of fluorine substitution by hydrogen in position 4. In perfluoro-tert-butylbenzene are substituted by hydrogen the fluorine atoms in positions 2 and 4; here the DMF-water ratio affects the regioselectivity of the process. In the perfluoro-4-tert-butyltoluene is mainly substituted the fluorine in the ortho-position to the C(CF₃)₃ group.     

The Albanese map of the Fano surface of a real M-cubic threefold

The restriction to the set of real points of the Albanese map of the Fano surface of a real M-cubic threefold is considered. Some topological properties of this map are proved.     

Nitration of Triazolyl-substituted Ketones

By nitration of 3-R-1,2,4-triazol-1-ylalkanones with a mixture of concentrated sulfuric and nitric acids a series of compounds was obtained containing a trinitromethyl fragment at the nitrogen of the ring.__________Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 5, 2005, pp. 767–771.Original Russian Text Copyright © 2005 by Kofman, Kartseva, Glazkova, Krasnov.     

Collapse of thermal activation in moderately damped Josephson junctions

We study switching current statistics in moderately damped Nb-InAs-Nb and intrinsic Bi2Sr2CaCu2O8+delta) Josephson junctions. A paradoxical collapse of thermal activation with increasing temperature is reported and explained by the interplay of two conflicting consequences of thermal fluctuations, which can both assist in premature escape and help in retrapping back into the stationary state. We analyze the influence of dissipation on the thermal escape by tuning damping with a gate voltage, magnetic field, temperature, and an in situ capacitor.