Cyanomethyl (CNMe) ether: an orthogonal protecting group for saccharides

Abstract

Logical manipulation of protecting groups is one of the vital strategies involved in the synthesis of complex oligosachharides. As opposed to the robust permanent protecting groups, the chemoselective protection–deprotection processes on orthogonal protecting groups have facilitated the synthesis of the target molecules with higher effeciency. While the derivatives of benzyl ethers are the most popular orthogonal ether based protecting groups for hydroxyls, the exploration of methyl ethers for similar synthetic application is much limited. We herein report cyanomethyl (CNMe) ether as a readily synthesized orthogonal protecting group for saccharides. The ether moiety was rapidly removed under Na-naphthalenide conditions in good to excellent yields and was found to be compatible with other well-known benzyl/methyl/silyl ether and acetal protecting groups. Additionally, the CNMe group was observed to be tolerant to standard reagents used for the deprotection of ether, ester and acetal protecting groups. The protection and deprotection steps remained unaffected by the position of hydroxyl, the configuration of monosaccharides or the presence of olefins in the skeleton.