Efficient Approach to the Azaspirane Core of FR 901483
摘要:
An efficient approach to the azaspirane core of FR 901483 is described employing lithiated methoxyallene as a crucial C3 building block and a suitably protected enantiopure ketimine as the second component. The resulting dihydropyrrole derivative was smoothly converted into a spiro keto aldehyde which under acidic conditions provided a novel azanorbornane derivative 15. Under basic reaction conditions, the desired 5-azatricyclo[6.3.1.0(1,5)] dodecane skeleton 16 was generated. The ratio of diastereomers strongly depends on the reaction conditions employed with L-proline in DMSO providing the highest selectivity in favor of one azaspirane product.
A concise enantioselectivesynthesis of the diazatricycliccore of alkaloidTAN1251C is reported. The method featured a stereoselective formation of the iodide intermediate 16b (in 2:1 ratio) from homoallylic amine 11b by iodine‐promoted iodoaminocyclization, a previously claimed to be unsuccessful reaction. The intermediate 16b was converted to the tricyclic core of TAN1251C 28 in five steps. During