Molecular sieves 5A as an acidic reagent: the discovery and applications

The first use of molecular sieves (MS) 5A as an acidic reagent is described. We observed the acidic property during a dehydration reaction of 2-methyl-4-phenyl-3-butyn-2-ol. The acidity was sufficient to introduce ethoxyethyl and methoxyisopropyl protecting groups into alcohols. Additionally, the employment of MS 5A improved the synthesis of 1,2,4-orthoacetyl-α-d-glucopyranose at the intramolecular transorthoesterification step. In the other step of the synthesis, MS 4A was also applied to demonstrate that the manipulation of MS simplified the total operations.