2-oxotetrahydroquinoline derivatives from Abelmoschus sagittifolius flowers

A phytochemical investigation of the flowers of Abelmoschus sagittifolius led to the isolation of three new 2-oxotetrahydroquinoline derivatives (1-3), together with three known compounds, namely fumaric acid (4), inosine (5), and guanosine (6). Their structures were elucidated by nuclear magnetic resonance (NMR) spectroscopy and high-resolution electrospray ionisation mass spectrometry (HR-ESI-MS). The absolute configurations of the new compounds were determined by electronic circular dichroism (ECD) calculation.