pyridine; ent-1α,13-diacetoxy-3α,10-dihydroxy-20-norgibberell-16-ene-7,19-dioic acid 7-methyl ester 19,10-lactone; hydrogen sulfide; N-ethyl-N,N-diisopropylamine 1.) dichloromethane, room temperature, 64 h; 2.) 5 min; Yield given. Multistep reaction;