Total syntheses of naturally occurring antiviral indolosesquiterpene alkaloids,xiamycins C–F via Csp3–H functionalization |
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Authors: | Mintu Munda Rhituparna Nandi Vipin R. Gavit Sourav Kundu Sovan Niyogi Alakesh Bisai |
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Affiliation: | Department of Chemistry, Indian Institute of Science Education and Research Bhopal, Bhopal Bypass Road, Bhopal 462 066 Madhya Pradesh India.; Department of Chemistry, Indian Institute of Science Education and Research Kolkata, Mohanpur Campus, Nadia, Kalyani 741 246 West Bengal India, |
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Abstract: | Concise total syntheses of naturally occurring antiviral indolosesquiterpene alkaloids, xiamycin C (2a), D (2b), E (2c) and F (2d), have been achieved via a late-stage oxidative δ-Csp3–H functionalization of an advanced pentacyclic enone intermediate 8. This strategy takes advantage of ipso-nitration of naturally occurring abietane diterpenoids to synthesize o-bromo nitroarene derivative 11. A Suzuki–Miyaura coupling of 11 with phenylboronic acid followed by Cadogan''s ring closure provided a modular approach to a carbazole ring required for a functionalized pentacyclic core of indolosesquiterpene alkaloids.Enantioenriched enone 8 was synthesized via three key transformations: ipso-nitration of abietane diterpenoids to furnish o-bromo nitroarene 11, Suzuki coupling with phenylboronic acid, and Cadogan''s reductive ring closure to craft a carbazole ring. |
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