Suggested Reaction 2.1.2.-

Left

Aconitane-4-methanol, 20-ethyl-7,8-(methylenebis(oxy))-, 1,6,14,16-tetramethoxy-2-(3-methyl-2,5-dioxo-1- pyrrolidinyl)benzoate(ester), (1-alpha,6-beta,14-alpha,16-beta)-
+THF

Right

Methyllycaconitine
+5,10-Methylene-THF

[BiSSCat | GREP ]