期刊
MOLECULES
卷 27, 期 15, 页码 -出版社
MDPI
DOI: 10.3390/molecules27154904
关键词
triterpenoids; betulinic acid; oxygen heterocycles; nitrogen heterocycles; diastereoselectivity; Michael addition
资金
- FEDER [POCI-01-0145-FEDER-016403]
- CICECO-Aveiro Institute of Materials [UIDB/50011/2020, UIDP/50011/2020]
- LAQV-REQUIMTE [UIDB/50006/2020]
- FCT/MCTES
- EpigenGlicON project [POCI-01-0145-FEDER-029767]
Betulinic acid was used as a starting material to synthesize a library of novel BA-derived compounds containing O- and N-heterocycles. Remarkably, the triterpene acts as a diastereoselective inducer in nitromethane conjugate addition reaction, and can also incorporate other heterocycles into its molecular structure using simple synthetic methods.
Betulinic acid (BA) was used as starting building block to create a library of novel BA-derived compounds containing O- and N-heterocycles. Firstly, BA was converted into methyl betulonate (BoOMe), which was used as intermediate in the developed methodologies. 1,2-Oxazine-fused BoOMe compounds were obtained in 12-25% global yields through a Michael addition of nitromethane to methyl (E)-2-benzylidenebetulonate derivatives, followed by nitro group reduction and intramolecular cyclization. Remarkably, the triterpene acts as a diastereoselective inducer in the conjugate addition of nitromethane, originating only one diastereomer out of four possible ones. Furthermore, other oxygen and nitrogen-containing heterocycles were installed at the A-ring of BoOMe, affording 2-amino-3-cyano-4H-pyran-fused BoOMe, diarylpyridine-fused BoOMe and 1,2,3-triazole-BoOMe compounds, using simple and straightforward synthetic methodologies. Finally, BA was revealed to be a versatile starting material, allowing the creation of a molecular diversification of compounds containing a triterpenic scaffold and O- and N-heterocycles.
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