Synthesis of triterpenoid-based ring-A azepanone and gem-3-nitro-3chloro-derivatives by ozonolysis of 3-oximino-28-oxoallobetulin under normal and acidic solvolysis conditionsстатьяИсследовательская статья
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Дата последнего поиска статьи во внешних источниках: 13 сентября 2017 г.
Авторы:Yamansarov Emil Yu,
Kazakova Oxana B.,
Medvedeva Natalya I.,
Lobov Alexander N.,
Suponitsky Kyrill Yu
Аннотация:It was found that ozonolysis of 3-oximino-28-oxoallobetulin under normal conditions (CHCl3, 0 degrees C) led to the preferred formation of azepanone (lactam) ring-A (61%) and partial removal of oximino-moiety to 28-oxoallobetulone (28%). In the case of ozonation under acidic conditions (5% vol. HCI in CHCl3, 0 degrees C) the attendant formation of minor products of 28-oxoallobetulin was observed, besides lactam (48%), with a total yield of 28%. These were 2,2-dichloroazepanone, (3S)-3-nitro-3-chloro-, 2-cyano-3,4-seco-4(23)en-, 2-cyano-3,4-seco-23-nor-4,28-dioxo-defivatives and also a mixture of A-seco-24-chlorine-contained products. 3-Nitro-3-chloro-28-oxoallobetulone was synthesized for the first time as a single (3S)-diastereoisomer with a yield of 9% in the reaction with ozone, while oxidation of 3-oximino-28oxoallobetulin with oxone in the presence of NaCI and H2O led to the mixture of (3R)-and (3S)-diastereomers. The application of ozone in the oxidative synthesis of ring -A lactams from 3-oximinotriterpenoids seems to be an alternative route to the Beckmann rearrangement.