TRANSFORMATION OF GRAYANOTOXIN-III TO 10-EPI-GRAYANOTOXIN-III - ITS X-RAY CRYSTALLOGRAPHIC ANALYSIS AND ACUTE TOXICITY IN MICE

Grayanotoxin(GTX) III, a tetracyclic diterpenoid, is the main toxic co mponent obtained from the leaves of Leucothoe grayana MAX. In this pap er, we report the correlation between toxicity and C-10 stereostructur e of CTX-III. 10-epi-GTX-III was derived from GTX-III in four steps. O xidation of the GTX-II-3,6,14,16-tetraacetate with formic acid/hydroge n peroxide in chloroform gave 10,20-epoxy derivative in high field. Re duction of the 10,20-epoxyacetate with LiAlH4 in tetrahydrofuran gave the two products, 10-epi-GTX-III and 10,20-epoxy-GTX-II. The absolute structure of the 10-epi-GTX-III was deduced from the results of X-ray crystallographic analysis. Dosage level of acute toxicity of 10-epi-GT X-III in mice was estimated at about half of natural GTX-III.