Reductive opening of carbohydrate phenylsulfonylethylidene (PSE) acetals

• Desulfonylation of carbohydrate phenylsulfonylethylidene (PSE) acetals is studied.
• Samarium iodide allows regioselective ring opening yielding 4-O-vinyl ethers.
• This reaction is applicable to a wide range of carbohydrate derivatives.
• PSE acetals might be useful as protective group.

The phenylsulfonylethylidene (PSE) acetal is a relatively new protecting group in carbohydrate chemistry. However, carbohydrate-derived phenylsulfonylethylidene (PSE) acetals show a different behavior in reductive desulfonylation than simple symmetrical acetals. Here we have investigated various SET-type reaction conditions in order to open PSE acetals regioselectively and to produce chiral ω-hydroxyethenyl ethers. Whereas sodium amalgam leads to a mixture of regioisomeric vinyl ethers besides the ethylidene acetal, samarium iodide is suited for regioselective ring opening. This is shown with seven different carbohydrate PSE acetals, both of the 1,3-dioxane and the 1,3-dioxolane type.

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