Conversion of Grayanotoxin III to Grayanotoxin V, Rhodojaponin III and Rhodojaponin IV

Abstract

Treatment of grayanotoxin (G) III with CH₃CHO in the presence of anhydrous CuSO₄ afforded a diethylidene compound (2). Oxidation of 2 (CrO₃) and subsequent ozonolysis and hydrolysis (KOH-MeOH) gave G-V (4) in 34% overall yield. Direct ozonolysis of 2 produced rhodojaponin (R) IV (8) in 68% yield. Δ²-Diethylidene compoud (10) was oxidized to 11, which on ozonolysis-hydrolysis furnished R-III (12) in 9.2% overall yield.