Stereoselective Preparation of the Tricyclic Hexasubstituted Spirocyclopropane Core of Cyclohelminthol X

This study focused on synthesizing
the tricyclic hexasubstituted
spirocyclopropane-core framework 2 of cyclohelminthol
X (1), an antifungal cytotoxin isolated from Helminthosporium velutinum yone96 in a stereoselective manner.
The synthesis features an SN2-type cyclopropanation of
the quaternary chloride 23 generated via a retro-Michael-type
ring-opening reaction of an 8-azatricyclo[4.3.0.12,5]deca-3,7,9-trione
derivative 22. The successful synthesis confirmed the
structure of 1, resolving the ambiguity from the absence
of X-ray crystallographic analysis. The prepared models exhibited
potent cytotoxicity.