178388-01-7Relevant academic research and scientific papers
C-Disaccharides of Ketoses
Streicher, Hansjoerg,Geyer, Armin,Schmidt, Richard R.
, p. 502 - 510 (2007/10/03)
Reaction of gluconolactone 2 with allylmagnesium bromide at low temperatures afforded ketopyranose 3, which could easily be converted into open-chain ketoses (R)-6 and (S)-6.Their reaction with lithioacetylide 9 afforded propargylic alcohol derivatives (R)-10 and (S)-10, which could not be cyclized directly to the desired C-ketosides.They were converted by standard procedures into (R)-14 and (S)-14 and then into dicobalthexacarbonyl complexes (R)-16 and (S)-16.A facile acid-catalyzed ring closure gave the desired C-ketosides (R)-18α/β and (S)-18α/β, respectively, in different ratios.In order to demonstrate that removal of the protective groups and hydrogenation of the CC triple bond proceed smoothly, (R)-18α was transformed into the deprotected target molecule (R)-1α.For the assignment of the new chiral centers at C-2/2' and at C-8, (S)-18α was transformed into azido derivative (S)-22α, which underwent intramolecular cycloaddition to afford the spiro derivative (S)-25α.Because of the conformational constraints in this molecule, unequivocal configurational assingnment was possible with the help of NMR data. - Keywords: alkynes; C-glycosides; cobalt complexes; cyclizations; enzyme inhibitors
