Base-catalyzed Degradations of Carbohydrates. II. β-Elimination Reactions of 4-<i>O</i>-Substituted Methyl (Methyl 2,3-Di-<i>O</i>-methyl-β-<scp>D</scp>-glucopyranosid)uronates

Abstract

The action of various bases on the three hexuronic esters, methyl (methyl 2,3,4-tri-O-methyl-β-D-glucopyranosid)uronate (12), methyl (methyl 4-O-methanesulfonyl-2,3-di-O-methyl-β-D-glucopyranosid)uronate (13), and methyl (methyl 4-O-acetyl-2,3-di-O-methyl-β-D-glucopyranosid)uronate (14), leading to elimination of the 4-O-substituents and formation of methyl (methyl 4-deoxy-2,3-di-O-methyl-α-L-threo-hex-4-enopyranosid)uronate (15) has been studied. It is concluded that effectiveness of 4-O-substituents as leaving groups is in the sequence, methanesulfonyloxy &gt; acetoxy &gt; methoxy.