Lewis Acid Promoted Deprotection of Benzylidene Acetals and p-Methoxybenzyl Ethers with Mercaptoacid Acid as Scavenger

Abstract

We demonstrate a new and high-yielding method for removal of benzylidene acetals and para-methoxybenzyl ethers under catalytic conditions (BF3:OEt2 orFeCl3, 10 mol%) with mercaptoacetic acid as a scavenger. The reaction coproducts are converted to water-soluble molecules, which can be removed by aqueous extraction, thereby bypassing the need for chromatographic purification. The reaction was demonstrated on both multimilligram and multigram scale.

Formation of β-Configured Thioglycosides ofd-Glucosamine andd-Galactosamine and Synthesis of Protected Human Milk Oligosaccharides

“…Next, the glycosylation was attempted on a lactose-based acceptor 15 , but this failed to give the desired product. The benzylidene was then removed by a recently developed and chromatography-free method using mercaptoacetic acid as a scavenger, and the resulting diol was protected by acetyl esters under standard conditions to give glycosyl donor 16 . This ( 16 ), however, also failed to give a tetrasaccharide in reaction with lactose-based acceptor 15 …”