We report a novel, facile, and asymmetric approach for the synthesis of the anti-tumor alkaloid (+)-crispine A via a highly diastereoselective N-acyliminium cyclization reaction as a key synthetic step.
Dedicated to Prof. Wilfred R. Chan for his inspiration and dedication to natural products chemistry. This paper describes the development of a highly stereoselective N-acyliminium cyclization protocol for the construction of a range of non-racemic heterocyclic templates. Due to the nature of this review, we have focused primarily on developments made within our own research group, but have included relevant and noteworthy contributions in the same area from others, most notably the research groups of Amat, Bosch and Lete. As a result, we apologize in advance for the omission of much excellent work carried out by many other talented researchers in this field.
We report a novel, facile, and asymmetric approach for the synthesis of polycyclic benzo[ a]quinolizidine targets. In the formation of more functionalized derivatives, we have observed the generation of an iminium ether salt intermediate, formed during an unprecedented retro-Diels-Alder/ N-acyliminium cyclization cascade. The iminium ether intermediate was isolated in good yield, characterized by X-ray crystallography, and subsequently applied as a synthetic building block.
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