Previously[1-4], we have reported on organocatalysed glycosylations using glycal donors and acceptors containing single unprotected hydroxy groups. This presentation will detail our efforts to effect regioselective and stereoselective glycosylations using organocatalysts and the differences observed when using diols as substrates compared to mono-ols. Galactose acceptors were chosen in order to systematically probe the regioselectivity of reactions with glycals.
Secondly, we will describe our efforts to use and combine Demchenko's concept of H-Bond-mediated Aglycone Delivery for stereoselective glycosylation[5], with Taylor's system for boron-mediated regioselective glycosylations[6] to effect stereo- and regioselective glycosylations. Some of these ideas have also been used in our efforts to design switchable 'bi-modal' donors[7,8], the results of which will be presented.
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