On the nitrile effect in l-rhamnopyranosylation

It is shown that the use of 5% acetonitrile or propionitrile in dichloromethane functions to increase the β-selectivity of a number of l-rhamnopyranosylation reactions conducted by the thioglycoside method with activation by the 1-benzenesulfinyl piperidine/trifluoromethanesulfonic anhydride couple. The use of more significant quantities of acetonitrile or propionitrile results in the formation of complex reaction mixtures containing little coupled product, but from which Ritter-type products can be isolated.

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