Dichlorolissoclimide, a new cytotoxic labdane derivative from Lissoclinum voeltzkowi Michaelson (Urochordata)

Spectral methods were used to determine the structure of a new cytotoxic compound, dicnlorolissoclimide 1, isolated from the New Caledonian ascidian #Lissoclinum voeltzkowi$ Michaelson. (Résumé d'auteur

Regioselectivity in the C-acylation of 2(3h)-benzoxazolones

Unequivocal synthetic routes towards 5- and 6-acyl-2(3H)-benzoxazolones are described. Comparison of the physicochemical properties of the compounds obtained by direct acylation under various Friedel-Crafts reaction conditions always leads to the conclusion that 6-acyl derivatives are the only isolated products. This observation contradicts previously published results

Effect of L-penicillamine Hydantoin, and Analog of Glutathione, On Rat-liver Glutathione-peroxidase, Reductase and Transferase Reactions

In soluble fractions prepared from rat liver homogenates, L-penicillamine hydantoin appeared to be, on the basis of SH consumption measurements, a substrate for glutathione peroxidase but not transferase reactions. When glutathione is incubated with rat liver soluble proteins in the presence of penicillamine hydantoin, formation of oxidized glutathione is inhibited. Calculations from Lineweaver-Burk plots point out that inhibition by L-penicillamine hydantoin of the peroxide-dependent oxidations of glutathione is mixed, since both apparent K(m) and V(max) values are modified. Preincubation of rat liver soluble proteins with L-penicillamine hydantoin led to a progressive inactivation of glutathione peroxidase. The kinetics of this inactivation process with respect to time and inactivator concentration were studied. Inclusion in the preincubation mixture of SH-containing molecules such as dithiothreitol, L-cysteine or glutathione protected the enzyme against inactivation. However, none of these molecules and neither hydantoin, Triton X-100, phenol, nor dialysis could reverse the enzyme from inactivated to activated form. Mitochondrial glutathione peroxidase was inhibited and inactivated by L-penicillamine hydantoin to the same extent as its cytosolic counterpart. Modifications by penicillamine hydantoin of various subcellular markers enzymes (lactate dehydrogenase, N-acetyl beta-glucosaminidase, arylsulfatase C, butyryl-CoA dehydrogenase, lauryl-CoA and glycolate oxidases) were of weak amplitude consisting of either inhibition, inactivation or stimulation