C-Lactam Derivatives of Oleanolic Acid. Hydrolysis and Further Acylation of Methyl Acetyloleanolate C-Lactam and C-Thiolactam

Abstract

Acetyl methyl oleanolate was transformed into a seven-membered C-lactam derivative (2) using Beckmann rearrangement of the corresponding C-oxime during the last step of the synthesis. The C=O group of the lactam system was transformed into a C=S group by Lavesson's reagent. The resulting acetylthiolactam 3 and initial acetyllactam 2 were subjected to alkaline hydrolysis to obtain lactam 4 and thiolactam 5 with an unsubstituted C-3 hydroxyl group. Subsequently, compounds 4 and 5 were acylated with either succinic or acetic anhydride in pyridine. Various acylating conditions were tested for hydroxythiolactam 5. The structures of the newly obtained compounds were supported by spectral and mass spectrometric data.