Recent Progress on Squaric Acid Research in Bioorganic Fields

Abstract

Squaric acid belongs to a class of oxocarbons and exhibits unique physicochemical properties, e.g., strong acidity, aromaticity, strained ring, electron deficiency, and metal chelating ability. Squaric acid has received considerable attention as a carboxylic acid mimic in medicinal chemistry, a novel chromophore in material science, a new chelator in inorganic chemistry, and a building block of quinones, triquinanes, cyclopentenones, and furanones in organic synthesis. Recently, squaric acid diesters are employed for a variety of applications in scientific fields as a linker to construct novel bioconjugate molecules. This review will describes recent progress on the use of squaric acid focused on bioorganic research.