Feldman Ken S, Antoline Joshua F
Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
Tetrahedron. 2013 Feb 4;69(5):1434-1445. doi: 10.1016/j.tet.2012.12.032.
The pentacyclic Melodinus alkaloid (±)-meloscine was synthesized in 19 chemical steps from 2-bromobenzaldehyde through a route featuring an allenyl azide cyclization cascade to deliver the core azabicyclo[3.3.0]octane substructure. Peripheral functionalization of this core included a Tollens-type aldol condensation to set the quaternary center at C(20) and a diastereoselective ring closing metathesis to forge the tetrahydropyridine ring.
五环马钱子生物碱（±）-马钱子碱以2-溴苯甲醛为原料，经19步反应合成，该路线的特点是烯丙基叠氮环化串联反应，构建核心氮杂双环[3.3.0]辛烷亚结构。该核心结构的外围官能团化包括Tollens型羟醛缩合反应以构建C（20）位的季碳中心，以及非对映选择性闭环复分解反应以形成四氢吡啶环。
