A biosynthetic proposal for ring formation in the antitumor agent halichomycin. Asymmetric synthesis of the AB-carbon backbone of halichomycin |
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Authors: | Hale Karl J Dimopoulos Paschalis Cheung Maxine L F Frigerio Mark Steed Jonathan W Levett Philip C |
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Affiliation: | The Christopher Ingold Laboratories, University College London, 20 Gordon Street, London WC1H 0AJ, England. k.j.hale@ucl.ac.uk |
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Abstract: | [reaction: see text] A biosynthetic proposal for ring formation in the antitumor agent halichomycin is presented in which macrocyclization of the putative prehalichomycin intermediate 1 is the first step. Compound 2 then undergoes dehydration to the alpha-keto N-acylimine 3 followed by tandem nucleophilic addition of the C(16)-hydroxyl to form the hemimacrolactam. A stereospecific Michael ring closure and enol protonation complete C-ring assembly. So far, synthetic efforts toward 1 have resulted in 8. |
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