Triterpenoide, 5. Synthese und Strukturaufklärung einiger neuer 18α-Oleanolsäurederivate
✍ Scribed by Zaprutko, Lucjusz ;Gzella, Andrzej ;Wrzeciono, Urszula
- Book ID
- 102902267
- Publisher
- John Wiley and Sons
- Year
- 1990
- Tongue
- English
- Weight
- 535 KB
- Volume
- 1990
- Category
- Article
- ISSN
- 0947-3440
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✦ Synopsis
Triterpenoids, 5. — Synthesis and Structure Elucidation of Some New 18α‐Oleanolic Acid Derivatives
On treatment with hydrogen bromide, 3β‐acetoxy‐11‐oxoolean‐12‐en‐28‐oic acid methyl ester (1) affords the expected 18α‐diastereomer 2 and the unknown 3‐isopropyl‐11‐oxo‐4‐nor‐18α‐oleana‐3(5),12‐dien‐28‐oic acid methyl ester (3) as product of a Wagner‐Meerwein rearrangement accompanied by the migration of the new introduced exocyclic double bond. Alkaline hydrolysis of 2 gives the known methyl ester 5 together with the new 3β,11‐dihydroxy‐12‐oxooleana‐9(11),13(18)‐dien‐28‐oic acid methyl ester (4). The byproducts 3 and 4 can also be obtained by treatment of 5 with acetic anhydride (3) or KOH/ethanol (4), respectively. The structure elucidation of 3 and 4 is described. The structure of 4 was confirmed by X‐ray analysis.