N-Benzyl-2,3-trans-Carbamate-Bearing Glycosyl Donors for 1,2-cis-Selective Glycosylation Reactions

Glycosyl donors for the preparation of 1,2-cis glycosides of amino sugars have been developed. The 2,3-trans-cyclic-carbamate-carrying glycosyl donors were readily prepared from the corresponding known trichloroethyl carbamate protected amino sugars under standard hydroxy group benzylation conditions. The donors exhibit high 1,2-cis stereoselectivity towards secondary hydroxy group substrates. In the case of primary hydroxy acceptors, high stereoselectivities were achieved with the aid of the dioxane effect. After glycosylation, the carbamate was removed under alkaline conditions. Importantly, these glycosyl donors can be used in polymer-supported and solid-phase synthesis.