ISSN:
0947-6539
Schlagwort(e):
alkynes
;
C-glycosides
;
cobalt complexes
;
cyclizations
;
enzyme inhibitors
;
Chemistry
;
General Chemistry
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
Notizen:
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)-18 α/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)-18 α was transformed into the deprotected target molecule (R)-1 α. 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 assignment was possible with the help of NMR data.
Zusätzliches Material:
1 Ill.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/chem.19960020508
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