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Modular Syntheses of Phenanthro­indolizidine Natural Products

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journal contribution
posted on 21.05.2019, 11:34 by Young-In Jo, Martin D. Burke, Cheol-Hong Cheon
A highly concise strategy for the total synthesis of phenanthro­indolizidines was developed. The one-pot iterative Suzuki–Miyaura reaction of aryl boronic acids with ortho-bromoaryl N-methyliminodiacetate (MIDA) boronate followed by a second Suzuki–Miyaura reaction with a suitable pyridyl bromide provided ortho-aza-terphenyls. Subsequent saturation of the triple bond, treatment with mesyl chloride, and reduction of the resulting dihydroindolizidinium ring afforded the hexahydroindolizines. A final vanadium-catalyzed oxidative electrocyclization provided the desired alkaloids in only three column-separation operations.