... Chemistry. ... The organic layer was evaporated and the residue was purified by preparative HPLC to give 22 (55 mg, 39 %) of as a yellow solid. mp: 117 °C; 1 H NMR (600 MHz, CDCl 3 ): enol tautomer (71 %) 6.96 (ddd, J=8.2, 7.2, 1.1 Hz, 1 H), 7.05 (dd, J=8.5, 1.1 Hz, 1 H), 7.00 (s ...