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Utilisation d'ylides du phosphore en chimie des sucres, X . Synthèse stéréospécifique de l'épimère en C3 du streptose et d'autres sucres ramifiés, dérivés de désoxy‐5‐pentoses, à groupements gem ‐hydroxy‐formyle ou gem ‐hydroxy‐hydroxyméthyle
Author(s) -
Tronchet J. M. J.,
Graf R.,
Gurny R.
Publication year - 1972
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19720550234
Subject(s) - chemistry , furanose , stereochemistry , hydroxymethyl , phosphorane , reagent , dihydroxylation , branching (polymer chemistry) , yield (engineering) , ketose , aldose , medicinal chemistry , ring (chemistry) , organic chemistry , glycoside , enantioselective synthesis , catalysis , materials science , metallurgy
The synthesis of branched‐chain sugars of the gem ‐hydroxy‐formyl and the gem ‐hydroxy‐hydroxymethyl types is described. A 5‐deoxy‐1,2‐O‐isopropylidene‐furanos‐3‐ulose is treated with cyanomethylene‐triphenyl‐phosphorane, yielding the two geometrical isomers of the corresponding branched‐chain unsaturated sugar. Cis ‐ dihydroxylation (KMnO 4 ) of these cyanomethylenic compounds affords stereoselectively and in high yield the gem ‐hydroxy‐formyl branched chain sugars whose formyl group is on the more hindered face of the furanose ring. The hydroxymethyl analogues of the latter compounds are readily prepared by their borohydride reduction. This method constitutes a new general route to type A branched‐chain sugars epimeric at the branching‐point with the sugars which would have been obtained by the classical procedure involving Grignard reagents.