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Exploiting Alkylquinone Tautomerization for the Total Synthesis of Calothrixin A and B
Luis M Mori-Quiroz1, Madeline M Dekarske1, Austin B Prinkki1
1Department of Chemistry, The University of Kansas , Lawrence, Kansas 66045, United States.
Abstract:
The pentacyclic alkaloid calothrixin B (1) has been synthesized in 5 steps from murrayaquinone A (9). The key step involved the union of boryl aniline 31 with brominated murrayaquinone A (26). In this transformation, alkylquinone 26 undergoes tautomerization to a quinone methide, which is intercepted by boryl aniline 31 to forge a new C-N bond. An intramolecular Suzuki coupling, followed by dehydrogenative aromatization, completed the synthesis of calothrixin B. Subsequent N-oxidation of calothrixin B delivered calothrixin A. The successful synthesis of these alkaloids and the challenges that led to the development of the final synthesis plan are reported herein.
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