The Use of Grignard Reagents in the Synthesis of Carbohydrates. II. The Cleavage of Acetal Protecting Groups in Sugar Derivatives

Abstract

Abstract The selective reaction of acetal protecting groups in sugars with Grignard reagents is described. The treatment of 1,2:5,6-di-O-cyclohexylidene-α-d-glucofuranose (1) with methylmagnesium iodide in benzene-ether at about 85 °C gave 1,2-O-cyclohexylidene-6-O-(1-methylcyclohexyl)-α-d-glucofuranose. When isopropylmagnesium iodide or t-butylmagnesium bromide was used instead of methylmagnesium iodide, 1 gave 1,2-O-cyclohexylidene-6-O-(cyclohex-1-enyl)-α-d-glucofuranose and the corresponding 6-O-cyclohexyl derivative. The selective cleavage of the acetal protecting groups in some other sugars with the Grignard reagents is also described.