New macrolide sesquiterpene alkaloids of Catha edulis: examples containing a novel dilactone bridge

The constitutions of three new sesquiterpene alkaloids, cathedulin-K19 (1)(C54H58N2O23, M 1 102), cathedulin-K17 (6)(C59H62N2O23, M 1 166), and cathedulin-K20 (8)(C59H62N2O23, M 1 166), obtained in small quantities from stems and leaves of Catha edulis(khat), have been demonstrated by spectroscopic examination. Alkaloids K17 and K19 contain a novel diester bridge derived from (Z)-4-(3-carboxy-2-pyridyl)-2-methylbut-3-enoic acid.