α-Selective Glycosylation with β-Glycosyl Sulfonium Ions Prepared via Intramolecular Alkylation.

Subsequent addition of glycosyl acceptor 21 (−78 °C to rt) led to the formation of disaccharides 22 – 29 in moderate to good yields ( Table 2 , entries 1–8). A clear trend of increasing α-stereoselectivity was observed with an increasing electron-donating character of the aryl group in both the gluco and galacto series.

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