The dimethoxyphenylbenzyl protecting group: an alternative to the p-methoxybenzyl group for protection of carbohydrates.

A reliable reagent system for the cleavage of 4-(3,4-dimethoxyphenyl)benzyl (DMPBn) ethers under acidic conditions has been established. Treatment of DMPBn-protected mono- and pseudodisaccharides with TFA in anhydrous CH2Cl2 and 3,4-(methylenedioxy)toluene as a cation scavenger resulted in the selective cleavage of the DMPBn ether giving the corresponding deprotected products in moderate to high yields. Examples are reported which show that allyl, benzyl, and p-bromobenzyl ethers, esters, and glycosidic linkages are stable to these reaction conditions. The selective cleavage of allyl, p-bromobenzyl, and PMB ethers in protected carbohydrates containing DMPBn ethers are also demonstrated. This work establishes the 4-(3,4-dimethoxyphenyl)benzyl ether as an effective and robust alternative to p-methoxybenzyl as a protecting group for alcohols.