Electrochemical reduction of phenylethynyl halides and related compounds

Reduction of phenylethynyl halides PhCCHal (Hal = I (1), Br (2), Cl (3)), diiodoacetylene (4), (phenylethynyl)triphenylphosphonium bromide (5), and related compounds in THF was studied by means of cyclic voltammetry using a glassy-carbon electrode. Compounds1–5 are reduced with cleavage of the C-Hal bond, and the reduction potentials increase in the order3 <2 <1 <4 <5.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2055–2057, October, 1995.     

Substituent effects on the nature of hydrogen bonding in organic hydroperoxides and the structure of triphenylmethyl hydroperoxide

It has been found that in the crystalline state in triphenylmethyl hydroperoxide the hydroperoxy group is involved in intermolecular hydrogen-bond formation of the type O-h..., with one C...C -bond in a benzene ring. Conformational analysis and comparison with the results of x-ray structural analysis leads us to conclude that there are very narrow limits on the possible conformations of the COOH group in tert-butyl, cumyl, 1,1-diphenylethyl, and triphenylmethyl hydroperoxides, independent of their aggregation state or the nature of the substituent attached to the COOH group.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 68–73, January, 1990.     

Effect of ginseng saponins on the survival of cerebral cortex neurons in cell cultures

The effects of nerve growth factor (NGF) and saponins isolated from Panax ginseng C.A. Mayer on the survival of chick and rat embryonic cerebral cortex neurons were examined. Ginsenoside Rg1 (GRg1) exerted a survival-promoting effect on both chick and rat cerebral cortex neurons in cell cultures. Ginsenoside Rb1 (GRb1) also had an effect in the rat and displayed some influence in the chick. NGF alone exerted no effect on both neurons, although it did potentiate the GRb1 effect on chick embryonic cerebral cortex neurons, but did not alter the GRb1 effect on rat embryonic cerebral cortex neurons. NGF did not alter the survival-promoting effect of GRg1 on either chick or rat embryonic cerebral cortex neurons. The other saponins alone or with NGF exerted no effect on the survival of cerebral cortex neurons in either the chick or rat.     

Carbon-13 NMR spectroscopy of heterocyclic compounds—III : A 20 MHz study of chemical shifts and carbon-proton coupling constants for the methyl coumarins

Complete assignments of chemical shifts and extensive assignments of carbon-proton coupling constants are presented for the 3-, 4-, 6-, 7- and 8-methylcoumarins, together with similar parameters for 5,8- and 6,8-dimethylcoumarin. Shifts in 6,8-dimethylcoumarin can be predicted with high precision from the substituent effects observed in the 6- and 8-methyl derivatives, and shifts are predicted for the 5-methyl derivative, which was not studied.