Norzoanthamine, an alkaloid isolated from Zoanthus sp., can suppress the loss of bone weight and strength in ovariectomized mice. Norzoanthamine derivatives can also strongly inhibit the growth of P-388 murine leukemia cell lines and human platelet aggregation. However, norzoanthamine's densely functionalized complex stereostructure and scarce availability from natural sources have proved a synthetic challenge. We report the stereoselective total synthesis of norzoanthamine in 41 steps, with an overall yield of 3.5% (an average of 92% yield each step).

The zoanthamine alkaloids, a type of heptacyclic marine alkaloid isolated from colonial zoanthids of the genus Zoanthus sp., have distinctive biological and pharmacological properties in addition to their unique chemical structures with stereochemical complexity. Namely, norzoanthamine (1) can suppress the loss of bone weight and strength in ovariectomized mice and has been expected as a promising candidate for a new type of antiosteoporotic drug, while zoanthamine (2) has exhibited potent inhibitory activity toward phorbol myristate-induced inflammation in addition to powerful analgesic effects. Recently, norzoanthamine derivatives were demonstrated to inhibit strongly the growth of P-388 murine leukemia cell lines, in addition to their potent antiplatelet activities on human platelet aggregation. Their distinctive biological properties, combined with novel chemical structures, make this family of alkaloids extremely attractive targets for chemical synthesis. However, the chemical synthesis of the zoanthamine alkaloids has been impeded owing to their densely functionalized complex stereostructures. In this paper, we report the first and highly efficient total syntheses of norzoanthamine (1) and zoanthamine (2) in full detail, which involve stereoselective synthesis of the requisite triene (18) for an intramolecular Diels-Alder reaction via the sequential three-component coupling reactions, the key intramolecular Diels-Alder reaction, and subsequent crucial bis-aminoacetalization as the key steps. Ultimately, we achieved the total synthesis of norzoanthamine (1) in 41 steps with an overall yield of 3.5 % (an average of 92 % yield each step) and that of zoanthamine (2) in 43 steps with an overall yield of 2.2 % (an average of 91 % yield each step) starting from (R)-5-methylcyclohexenone (3), respectively.

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Cell extrusion is a universal mode of cell removal from tissues, and it plays an important role in regulating cell numbers and eliminating unwanted cells, such as apoptotic, unfit, or cancerous. During this process, cells delaminate from the cell layer, however, the underlying mechanisms remain to be elucidated. Here, we report a conserved execution mechanism of cell extrusion. We found extracellular vesicle (EV) formation in extruding cells at a site opposite to the extrusion direction. Particularly, we found that a lipid-scramblase‒mediated local exposure of phosphatidylserine is responsible for EV formation and is crucial for executing cell extrusion, while inhibition of this process disrupted prompt cell delamination and tissue homeostasis. Furthermore, we revealed that the EV formation is governed by the mechanism in microvesicle formation, while the EVs have some hallmarks of apoptotic body. Finally, we illustrated the role of EV formation as promoting the neighboring cells’ invasion resulting in the execution of cell extrusion by experimental and mathematical modeling analysis. Taken together, this study provides the insights that membrane dynamics plays a crucial role behind the cell exit from the tissue by connecting the actions of extruding cell and the neighboring cells.

Numerous unwanted cells are removed from epithelial and endothelial tissues—in which cells are tightly connected to one another—without disturbing tissue integrity and homeostasis. Cell extrusion is a unique mode of cell removal from tissues, and it plays an important role in regulating cell numbers and the eliminating unwanted cells, such as apoptotic cells, cancer cells, and cells with a lower fitness in cell competition . During this process, cells delaminate from the cell layer, to which they initially used to adhere, through communication with the neighboring cells. Defects in cell extrusion are believed to associate with inflammation and cancer in epithelium as well as blood vessel dysfunction. However, the correlation between them has not yet been evaluated owing to a lack of knowledge of the underlying mechanisms. In particular, the process whereby the cell exit from the tissue remains to be elucidated. Here, we report a novel and conserved execution mechanism of cell extrusion—common to mammalian cells and Drosophila epithelia—i.e., spatiotemporally regulated extracellular vesicle formation in extruding cells at a site opposite to the direction of extrusion. Particularly, we found that a lipid-scramblase‒mediated local exposure of phosphatidylserine is responsible for extracellular vesicle formation and is crucial for the execution of cell extrusion, and inhibition of this process disrupted prompt cell delamination as well as tissue homeostasis. Furthermore, we revealed the mechanism underlying vesicle formation. Importantly, our results reveal that membrane dynamics is the driving force by a “rocket launch”-like mechanism behind the extrusion of cells from tissues, a fundamental cell behavior in multicellular organisms that is also observed in other contexts including cancer cell invasion and neural cell differentiation. Our understanding of this new mechanism of cell extrusion enables us to examine the relationship between cell extrusion abnormalities and the onset of various diseases.