Utilizing a Mild and Effective Catalyst, Alum (KAl(SO4)2⋅12H2O), for Carbohydrate Protection

Abstract

AbstractThis study aimed to optimize the per‐O‐acetylation, deacetylation, and benzylidene protection of carbohydrates and investigate the scope of saccharides via alum‐catalysis. Initially, optimization was based on the previously reported PTA‐catalyzed acetylation of glucose, but alum‐catalysis required heating conditions. The study expanded to investigate the per‐O‐acetylation of different saccharides, including galactose and mannose, which produced stereoisomeric mixtures. The study proposed a plausible reaction mechanism for the isomerization observed in galactose and xylose after acetylation. The mechanism involved chelation of the active alum‐catalyst with the O‐6 position and β‐type O‐1 position of galactopyranose to form a transition state complex via ring opening. This study investigated the generality of the de‐O‐acetylation method on a variety of carbohydrates using per‐O‐acetyl saccharide substrates bearing different functional groups. The direct protection of benzylidene in addition to acetylation/de‐O‐acetylation with a focus on optimizing reaction conditions for the synthesis of carbohydrate derivatives. Overall, the study offers insights into optimizing de‐acetylation, per‐O‐acetylation, and benzylidene protection investigating the scope of saccharides via alum‐catalysis.