Functionalization of polysaccharides are of great interests in enhancing the desired properties of polysaccharide derivatives for purposes as diverse as drug delivery, antimicrobial, and coating. However, such efforts have relied extensively on conventional synthetic approaches such as esterification and etherification. While the convention methods have indeed contributed to most commercially important polysaccharide derivatives, the diversity of these derivatives are, however, limited by these methods due to harsh conditions they require, and/or accessibility of reagents. Olefin cross-metathesis (CM) has, for the first time, been used for polysaccharide modification (cellulose in particular), and proven a mild, modular and wide in scope approach. Generally, cellulosic backbones were appended with terminally olefinic side-chains as handles (e.g. cellulose acetate undec-10-enoate), which was then reacted with a CM partner via CM, and thus functionalized with corresponding functional group (Figure 1). By switching to a variety of different acrylic acid-based CM partners such as acrylic acid and acrylates, efficient, modular and wide in scope side-chain functionalization of cellulose can be achieve. This chemistry is so mild and efficient that under room temperature nearly 100% of terminal olefin can be converted to CM adducts within 1 h in most reactions. Considering that the α,β-unsaturation may lead to crosslinking of the CM products due to a free radical mechanism, we explored reactions including hydrogenation that reduce the unsaturation and thus eliminate the potential instability. With this chemistry in the toolkit of polysaccharide chemists, we believe more and more polysaccharide derivatives with diverse functionalities and facile synthetic pathways will be obtained.

Olefin cross-metathesis, a mild, modular and efficient approach towards functionalized cellulose esters

249th National Meeting (2015)

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