Methanol → (S)-1-isopropyl-5-oxopyrrolidine-2-carboxylic acid

Methyl 1-(1-methylethyl)-5-oxo-prolinate (0.152 g, 0.82 mmol) was dissolved in water (3 ml) and methanol (0.5 ml) and treated with 2M aqueous sodium hydroxide (0.682 ml, 1.36 mmol). The mixture was stirred for ˜4 hrs at room temperature and then washed with dichloromethane. The aqueous layer was evaporated and the residue treated with an excess of 1M hydrogen chloride in ether (˜5 ml). The mixture was evaporated once more and the residue was triturated with dichloromethane. The solid material was discarded and the combined dichloromethane fractions were evaporated to give 1-(1-methylethyl)-5-oxo-proline (0.060 g) as a yellow oil which crystallized on standing.