New monoterpenoid alkaloids from the aerial parts of Uncaria hirsuta

To investigate the chemical constituents of medicinal plant Uncaria hirsuta, three new monoterpenoid alkaloids, named hirsutanines A–C (1–3), were isolated. Their structures with absolute configurations were elucidated by means of NMR, X-ray diffraction and CD analysis. Compound 3 was the first dimeric monoterpenoid alkaloid obtained from genus Uncaria.