Photoöxidation of oleanolic acid: formation of 11α, 12α-epoxy- and 12α-hydroxy-oleanolic lactones

✍ Scribed by Isao Kitagawa; Kiyoshi Kitazawa; Itiro Yosioka

• Publisher: Elsevier Science
• Year: 1968
• Tongue: French
• Weight: 202 KB
• Volume: 9
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(01)98794-5

✦ Synopsis

In 1965, Corey and his co-workers reported 1) an interesting paper on the oxidative rearrangement of pentecyclic triterpenes which involved a novel skeletal rearrangement of thermodynamically more favored 8-amyrin (I) towards less stable taraxerene derivative (II) by way of photochemical oxidative procedure in the acidic medium. They proposed sn intermediate (III) in connection with the independent synthesis of the same product (II) starting from I by the alternate chemical oxidation. we assumed that if I carries 17-COOE function in place of 17XR3 as in oleanolic acid (IV), it would be appropriate to expect participation of the cerboxylic function at the stage of intermediate (es in V) resulting lla,l2a-epoxy-clesnolic lectone (VI) as a final product. On the other hand. a unique nortriterpenoid named eupteleogenin (VII) 2,3) , a sapogenin of the biological active saponin,is so far * TLC of the total mixture disclosed the formation of small amount of oleanolic lactone (VI, without epoxy function), which was, bowever, not isolated in a pure state. ** Based on the pure compound obtained. *** Measured et 100 Mc. in CDCI....