- A new approach to some 1,6-dideoxy 1,6-epithio sugars
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The treatment of hexopyranosyl bromides, also activated at C6 (Br, OTs, OMs), with H2S/HCONMe2 under basic conditions gives rise to 1,6-dideoxy 1,6-epithio sugars. One such sugar has been further transformed into the synthetically useful 3,4-anhydro-1,6-dideoxy-1,6-epithio-β-D-galactose. The treatment of this epoxide with sodium azide and with cyclohexylamine is described. An analogous treatment of one doubly activated hexopyranosyl bromide with sodium hydrogen selenide has led to a novel 1,6-dideoxy 1,6-episeleno sugar which displayed interesting n.m.r. spectra. Finally, in an attempt to prepare 1,6-dideoxy 1,6-epidithio sugars, a tetraalkylammonium tetrathiomolybdate reagent was found to be the reagent of choice for converting doubly activated hexopyranosyl bromides into 1,6-dideoxy 1,6-epithio sugars.
- Driguez, Hugues,McAuliffe, Joseph C.,Stick, Robert V.,Tilbrook, Matthew G.,Williams, Spencer J.
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p. 343 - 348
(2007/10/03)
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- Synthesis of glycyrrhetic acid diglycosides and their cytoprotective activities against CCl4-induced hepatic injury in vitro
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Glycyrrhetic acid diglycosides 16, 24, 25, 42 and 46, with respectively β-D-glucuronopyranosyl-(1→3)-β-D-glucopyranose, -(1→6)-α-D-glucopyranose, -(1→6)-β-D-glucopyranose, -(1→6)-β-D-galactopyranose, and β-D-galacturonopyranosyl-(→2)-β-D-glucopyranose as sugar components at the O-3 positions on the aglycons, were synthesized. In vitro cytoprotective activities, against CCl4-induced hepatic injury, of the synthetic diglycosides, methyl β-D-glucuronopyranosyl-(1→4)-α-D-glucopyranosyl-D-glycyrrhe tinate 33 and methyl esters 15 and 23 (the precursors of 16 and 24 respectively) were compared with those of glycyrrhizin 1 and β-D-glucuronopyranosyl-(1→2)-β-D-glucopyranosyl-glycyrrhetic acid 2. Of the glycosides 16, 24, and 25, with β-D-glucuronopyranosylglucopyranose as the sugar component, 16 and 24 were as cytoprotective as 1 and 2, whereas 25 showed no remarkable activity. From stereomodels of the glycosides these differences in activity were inferred to be due to the stereochemistries of the terminal β-D-glucuronopyranoses in the molecules. Glycoside 46, in which the terminal β-D-glucuronopyranose of 2 was replaced by β-D-galacturonopyranose, was as potent as 2. Further, it was confirmed that a free COOH group on the E ring of aglycon was essential for the activity.
- Saito,Nagase,Kawase,Nagamura
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p. 557 - 574
(2007/10/03)
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