Synthesis of novel lupane triterpenoid-indazolone hybrids with oxime ester linkage
Tatyana S Khlebnicova1, Yuri A Piven1, Alexander V Baranovsky1
1Institute of Bioorganic Chemistry, National Academy of Sciences of Belarus, Acad. Kuprevicha Str. 5/2, 220141 Minsk, Belarus.
Abstract:
An efficient protocol for the synthesis of novel lupane triterpenoid-indazolone hybrids with oxime ester linkage has been developed from naturally accessible precursor betulin. For the first time a series of betulonic acid-indazolone hybrids have been synthesized via an acylation of corresponding 6,7-dihydro-1H-indazol-4(5H)-one oximes with betulonic acid chloride. Diastereoselective reduction of the obtained betulonic acid conjugates with NaBH4 resulted in a formation of betulinic acid-indazolone hybrids in excellent yields. The configuration of the key compounds has been fully established by X-ray and 2D NMR analysis.
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