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Description:
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Palau'amine is a natural product originally isolated in 1993 from the marine sponge Stylotella aurantium . It is reported to posess impressive biological activities , including : antifungal , antibacterial , and antineoplastic characters . Moreover , it is a strong immunosuppressant (IC50 <18ng /mL , allogenic lymphocyte reaction ) . The molecule has a complex polycyclic structure having a contiguous array of eight stereogenic centers . It is unusually rich in heteroatoms . A recent revision of its relating stereochemistry has brought further attention to this fascinating molecule . The current strategy of our group features a chlorination initiated cascade process on a symmetric precursor that assembles the skeleton of palau'amine with in a single operation . A symmetric bisalkylidene precursor for this process was synthesized . During the process , two new methodologies were developed : a titanocene dichloride mediated regioselective and stereoselective dimerization of heterocyclic dineolates ; and a chemoselective Rh (I ) carbene complexes catalyzed conjugation hydrosilylation of enamides . Our core idea was subsequently validated by the formation of the spirocyclopentane motif in palau'amine by an electrophilic halogen induced desymmetrization . |