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TOTAL SYNTHESIS OF STEMONA ALKALOIDS VIA PALLADIUM CATALYZED CARBONYLATION
thesisposted on 2021-10-12, 15:07 authored by Xianglin YinXianglin Yin
Carbon monoxide is a useful carbon linchpin to construct complex molecules of natural products by stitching different pieces of target molecules together. Recently, our group reported a novel and efficient palladium-catalyzed spirolactonization by Dr. Dexter Davis to construct oxaspirolacones from esters or lactones. As an essential motif, oxaspirolactone structures in natural products exhibit diverse and exciting structures and biological activities. The first part of this thesis mainly describes the total synthesis of stemoamide alkaloids in the stemona family and the application of our palladium-catalyzed spirolactonization, which was developed by our group to complete total synthesis of bisdehydroneostemoninine and bisdehydrostemoninine with Prof. Kaiqing Ma. The total synthesis features a one-pot ring-closing cross-metathesis, Lewis acid-mediated Friedel-Crafts reaction and lactonization, and accomplished bisdehydrostemonine in 15 steps. The total synthesis of stemoamide, tuberostemoamide, and sessilifoliamide A were finished, and the critical step features an mCPBA oxidation to convert pyrrole to lactam in one step without destructing other functional groups.
In the second part of this thesis, we developed a novel and efficient palladium-catalyzed cascade amino-carbonylative lactonization to streamline the synthesis of dihydropyrrole-fused furanones in collaboration with Prof. Seleem’s lab for biological activities. Using this method, we quickly expanded this method to construct different ring structures, such as β-lactone and dihydropyrrole-fused pyrrolone. This method was applied to the total synthesis study towards stemofoline alkaloids. Our palladium-catalyzed spirolactonizaiton was also used in this total synthesis study for target molecules.