Influence of protecting groups on O- and C-glycosylation with neuraminyl and ulosonyl dibutylphosphates.
Carbohydr Res
; 496: 108100, 2020 Oct.
Article
in En
| MEDLINE
| ID: mdl-32755675
ABSTRACT
The adamantanyl thioglycosides of 5-isothiocyano and 5-azido 5-desamino-4,7,8,9-tetra-O-acetylneuraminic acid methyl ester were converted into the corresponding dibutyl phosphates, which proved to be excellent α-selective donors for O-sialidation with a range of typical acceptors, and good donors for reaction with allyltributylstannane, albeit without significant anomeric selectivity. In the KDN series the dibuylphosphate derived from a donor carrying a 4,5-cyclic carbonate protecting group afforded the corresponding C-glycoside with excellent α-selectivity on activation in the presence of allyltributylstannane, whereas the corresponding donor carrying acetate esters at the 4- and 5-positions was unselective. Overall, it is revealed that while the strongly electron-withdrawing isothiocyanato and azido groups are sufficient to promote highly α-selective O-sialidation, they are inadequate when faced with less reactive nucleophiles when mixtures of anomers are obtained.
Key words
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Oxygen
/
Phosphates
/
Carbon
Language:
En
Journal:
Carbohydr Res
Year:
2020
Type:
Article
Affiliation country:
Japan