- Perfectly regioselective acylation of a cardiac glycoside, digitoxin, via catalytic amplification of the intrinsic reactivity
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Organocatalytic regioselective acylation of digitoxin has been developed. This method provides the 4′′′-O-manoacylate as the sole product without the concomitant formation of diacylates. The extremely high regioselectivity was assumed to be the result from the combined effects of the high intrinsic reactivity of C(4′′′)-OH and catalyst-promoted regioselective acylation of the same hydroxy group.
- Yoshida, Keisuke,Furuta, Takumi,Kawabata, Takeo
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p. 4830 - 4832
(2010/10/02)
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- Uses of ouabain and ouabain-like molecules in apoptosis related pathologies
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Longterm elevation of the intracellular Na+/K+ratio inhibits macromolecule synthesis and proliferation in the majority of cell types studied so far, including vascular smooth muscle cells (VSMC). We report here that inhibition of the Na+,K+pump in VSMC by ouabain or 1 hour preincubation in K+-depleted medium attenuated apoptosis triggered by serum withdrawal, staurosporine or okadaic acid. In the absence of ouabain, both DNA degradation and caspase-3 activation in VSMC undergoing apoptosis were insensitive to modification of the extracellular Na+/K+ratio as well as to hyperosmotic cell shrinkage. In contrast, protection of VSMC from apoptosis by ouabain was abolished under equimolar substitution of Na+owith K+o, showing that the anti apoptotic action of Na+,K+pump inhibition was caused by inversion of the intracellular Na+/K+ratio. Unlike VSMC, the same level of increment of the [Na+]i/[K+]iratio caused by 2 hours preincubation of Jurkat cells with ouabain did not affect chromatin cleavage and caspase-3 activity triggered by treatment with Fas ligand, staurosporine or hyperosmotic shrinkage. Thus, our results show for the first time that similarly to cell proliferation, maintenance of a physiologically low intracellular Na+/K+ratio is required for progression of VSMC apoptosis.
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