On the synthesis of N-maleoyl amino acids in aqueous media: cautionary tales for the unwary traveller

The high cost or protracted syntheses associated with N-maleoyl amino acid derivatives coupled with a considerable demand from both the life and physical sciences has spurred the search for facile, low-cost routes to these compounds. Herein, we demonstrate that a recently published method purporting to deliver N-maleoyl amino acids by cyclization of maleamic acids in water, instead results in a hydrolysis product, namely the corresponding hemi-maleate salt.