A 3,4-trans-fused cyclic protecting group facilitates α-selective catalytic synthesis of 2-deoxyglycosides
Edward I Balmond1, David Benito-Alifonso, Diane M Coe
1School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS (UK).
Abstract:
A practical approach has been developed to convert glucals and rhamnals into disaccharides or glycoconjugates with high α-selectivity and yields (77-97%) using a trans-fused cyclic 3,4-O-disiloxane protecting group and TsOH⋅H2O (1 mol%) as a catalyst. Control of the anomeric selectivity arises from conformational locking of the intermediate oxacarbenium cation. Glucals outperform rhamnals because the C6 side-chain conformation augments the selectivity.
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