2-Methyl-6-nitrobenzoic anhydride

2-Methyl-6-nitrobenzoic anhydride is an organic acid anhydride also known as the Shiina reagent, having a structure wherein carboxylic acids undergo intermolecular dehydration condensation. It was developed in 2002 by Prof. Isamu Shiina (Tokyo University of Science, Japan). The compound is often abbreviated MNBA.

Abstract
The reagent is used for synthetic reactions wherein medium- and large-sized lactones are formed from hydroxycarboxylic acids via intramolecular ring closure (Shiina macrolactonization). The reaction proceeds at room temperature under basic or neutral conditions. This reagent can be used not only for macrolactonization but also for esterification, amidation, and peptide coupling.