Activation of glycoyl trihaloacetimidates with acid-washed molecular sieves in the glycosidation reaction.

[reaction: see text] Commercially available 4 A acid washed molecular sieves (4 A AW 300 MS) are efficient activators of glycosyl trichloro- and N-phenyltrifluoroacetimidates. These promoters allow glycosidation of primary and secondary saccharidic acceptors to be performed in high yield, under very mild conditions and by an experimentally simple procedure. In addition, the recyclability of such promoters also has been demonstrated.