Assessing the effectiveness of different chiral and achiral phosphoric acids in presence of thiourea co-catalyst in co-operative organocatalytic stereoselective glycosylation reactions

摘要

Organocatalytic glycosylation reactions were attempted with an aim to achieve stereoselectivity using chiral TRIP (Binol derived phosphoric acid) and achiral biphenyl phosphoric acids as catalyst and a thiourea derivative as co-catalyst, based on the transition model suggested by Schmidt group([1]) during co-operative organocatalysis. Though the stereoselectivity as reported by the Schmidt was not observed, but it was found that the thiourea co-catalyst assisted the catalyst in making the reaction faster, especially in the cases where the catalyst was itself not a strong enough acid.