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Friedelane triterpenoids: transformations toward A-ring modifications including 2-homoderivatives

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Abstract

Friedelin and its derivatives, commonly known as friedelane triterpenoids, exhibit potential biological effects ranging from antimicrobial to anticancer to anti-HIV. To modify the A-ring of the pentacyclic triterpenoid, various transformative scopes have been utilized. Herein, some simple unprecedented transformative protocols have been accomplished towards furnishing 42 (25 new) A-ring modified pentacyclic friedelane triterpenoids. It is worth noting that the modifications include the all-new 2-homo derivatives. The one-pot BF3·OEt2-mediated oxidative transformation of friedelin to yield friedel-3-enol acetate as the major product was one of the key reactions. A group of isomeric A-ring modifications was produced on the basis of simple transformations on suitable friedelane-based molecules. The syntheses of the novel 2-homofriedelanes were envisioned from the transformative reactions of the designed triterpenoid 3-chlorofriedel-2-ene-2-carbaldehyde, which was isolated as the major product from the reaction of friedelin with the novel Vilsmeier–Haack reagent. New A-ring modified derivatives were also obtained due to further interesting transformations of 3-chlorofriedel-3-ene, isolated as side products from the same reaction. Again, considering the scope of the 3-chloro-2-enal moiety associated with the A-ring of the triterpenoid, some heterocycle-linked- (bonded to C3) 2-homofriedelane triterpenoids were synthesized. Various common reaction strategies were employed on suitable substrates to finally achieve a series of C2,C3-; C3,C4- and C2,C3,C4-functionalized as well as 2-homofriedelane triterpenoids with just one to four efficient steps.

Graphical abstract: Friedelane triterpenoids: transformations toward A-ring modifications including 2-homoderivatives

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Publication details

The article was received on 01 Jan 2018, accepted on 05 Mar 2018 and first published on 06 Mar 2018


Article type: Paper
DOI: 10.1039/C8NJ00009C
Citation: New J. Chem., 2018, Advance Article
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    Friedelane triterpenoids: transformations toward A-ring modifications including 2-homoderivatives

    J. Das, A. Sarkar and P. Ghosh, New J. Chem., 2018, Advance Article , DOI: 10.1039/C8NJ00009C

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