Side reactions isonitrile complexes

The high stereoselectivity can be explained again by means of the zinc complex A (see Scheme 3). The nucleophilic isonitrile attacks the glycosyl imine from the steri-cally less shielded Re-side. The bulky pivaloyl group at the 2-position and the formed zinc complex block the Si-side efficiently. The exchange of the pivaloyl for the acetyl group decreases the selectivity of the reaction (10 1 instead of 30 1) [13]. 

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