We report herein the asymmetric total synthesis of norzoanthamine using radical reactions as key steps for rapid access to the congested carbocyclic core, which is the major synthetic challenge for most zoanthamine alkaloids. (1) The Ueno–Stork radical cyclization was applied to construct the adjacent quaternary centers at the C-9 and C-22 positions; (2) a Co-catalyzed HAT radical reaction was successfully applied to construct the quaternary center at C-12 via Csp3-Csp2 bond formation; (3) a Mn-catalyzed HAT radical reaction was used to stereospecifically reduce the tetra-substituted olefin (C13=C18) and install the contiguous stereocenters in proximity to the quaternary center. A one-pot bio-inspired cyclization step was finally applied to forge the unstable bis-amino acetal skeleton. Our approach can precisely control the stereochemistry of seven vicinal stereocenters and effectively construct the highly congested heptacyclic skeleton.
Structure-activity relationship of norzoanthamine exhibiting significant inhibition of osteoporosis
Norzoanthamine is a zoanthamine-type alkaloid from the colonial zoanthid Zoanthus sp. Norzoanthamine hydrochloride, which suppresses the decrease in bone weight and strength in ovariectomized mice, could be a good candidate for an osteoporotic drug. Although the relative configuration of norzoanthamine was established based on an X-ray crystallographic analysis, the absolute stereochemistry of norzoanthamine remains unclear. To investigate their biogenesis and mechanisms of biological action, we conducted chemical and spectroscopic studies to determine the absolute configuration of norzoanthamines.
Synthetic studies of the Zoanthamine alkaloids: Total synthesis of zoanthenol based on an isoaromatization strategy
The total synthesis of zoanthenol, a unique aromatic member of the zoanthamine alkaloids, which has exhibited potent anti-platelet activities on human platelet aggregation, is described in full detail. The key step involves a Bronsted acid-promoted isoaromatization in the AB ring system to install the crucial aromatic ring. We have not only succeeded in the first total synthesis of zoanthenol, but also established an alternative efficient synthetic route from the commercially available norzoanthamine hydrochloride to zoanthenol. The mask of zoanthenol: The total synthesis of zoanthenol is described in full detail. Zoanthenol is an aromatic member of the zoanthamine alkaloids and it has potent anti-platelet activity for human aggregation. The key step involves a Bronsted acid-promoted isoaromatization in the AB ring system to install the crucial aromatic ring (see scheme).
Reaching home plate: The first total synthesis of zoanthenol, an aromatic member of the zoanthamine alkaloid family with potent anti-platelet activity for human platelet aggregation, has been achieved using an intermediate in the total synthesis of norzoa
No bones about it: (-)-Norzoanthamine, a promising candidate for an anti-osteoporotic drug, was the target of a total synthesis (see scheme). The final bisaminal formation with AcOH/H2O gave the DEFG ring, while the cyclization precursor was pr
Method for producing zoanthamine alkaloid and intermediate used in same
The present invention provides a method for producing a zoanthamine alkaloid and an intermediate suitably used in the method. The method realizes high-yield synthesis of a zoanthamine alkaloid such as norzoanthamine or the like.
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(2010/10/19)
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