Thioesterification

Thioesterification is a chemical reaction that forms a thioester functional group. A thioester has the general structure R-C(=O)-S-R', where R and R' are alkyl or aryl groups. This linkage is analogous to an ester linkage (R-C(=O)-O-R'), but with sulfur replacing oxygen in the part derived from the alcohol. The reaction typically involves activating a carboxylic acid and then reacting it with a thiol. Common activating agents include carbodiimides like dicyclohexylcarbodiimide (DCC) or coupling reagents used in peptide synthesis. Alternatively, a pre-formed activated carboxylic acid derivative, such as an acyl halide or anhydride, can react directly with a thiol. Thioesters are important in biochemistry, particularly in the biosynthesis of fatty acids and polyketides, where they serve as activated intermediates. For example, acetyl-CoA and malonyl-CoA are crucial thioesters in metabolism. The C-S bond in thioesters is weaker and more reactive than the C-O bond in esters, making them good acyl group donors in various enzymatic reactions. This reactivity is often exploited in organic synthesis to create complex molecules.