Benzylidene Acetal Protecting Group as Carboxylic Acid Surrogate: Synthesis of Functionalized Uronic Acids and Sugar Amino Acids. Issue 3 (7th December 2015) - Banerjee, Amit
Abstract: Direct oxidation of the 4, 6‐ O ‐benzylidene acetal protecting group to C‐6 carboxylic acid has been developed that provides an easy access to a wide range of biologically important and synthetically challenging uronic acid and sugar amino acid derivatives in good yields. The RuCl3 –NaIO4 ‐mediated oxidative cleavage method eliminates protection and deprotection steps and the reaction takes place under mild conditions. The dual role of the benzylidene acetal, as a protecting group and source of carboxylic acid, was exploited in the efficient synthesis of six‐carbon sialic acid analogues and disaccharides bearing uronic acids, including glycosaminoglycan analogues. Abstract : Easily done : Upon exposure to the RuCl3 –NaIO4 reagent system, 4, 6‐ O ‐benzylidene acetal protecting groups undergo a facile oxidative cleavage to furnish a wide range of biologically important and structurally diverse uronic acid and sugar amino acid derivatives in good yields under mild conditions (see scheme; Phth=phthaloyl; Bz=benzoyl; TBDMS= tert ‐butyldimethylsilyl; Ts=tosyl).