Ipomoeassins A-E, cytotoxic macrocyclic glycoresins from the leaves of Ipomoea squamosa from the Suriname rainforest

The new glycoresins, ipomoeassins A-E (1-5), have been isolated from the leaves of Ipomoea squamosa. The structures were elucidated by spectroscopic analyses and chemical transformations. The absolute configurations of C-5 (ipomoeassins 3-5) and C-11 (ipomoeassins 1 and 2) were determined by their derivatives with (R)- and (S)-MPA. All the isolates were active in the A2780 human ovarian cancer cell line assay, and 4 showed the highest activity with an IC(50) value of 35 nM.