Allenyl Azide Cycloaddition Chemistry: Application to the Total Synthesis of (±)-Meloscine
摘要:
The pentacyclic alkaloid (+/-)-meloscine was prepared in 19 steps through a reaction sequence that features a putative azatrimethylenemethane intermediate, generated through cascade cyclization of an allenyl azide substrate, to deliver the core azabicyclo[3.3.0]octadiene substructure. Subsequent manipulation of the peripheral functionality then delivered (+/-)-meloscine.
Allenyl Azide Cycloaddition Chemistry: Application to the Total Synthesis of (±)-Meloscine
摘要:
The pentacyclic alkaloid (+/-)-meloscine was prepared in 19 steps through a reaction sequence that features a putative azatrimethylenemethane intermediate, generated through cascade cyclization of an allenyl azide substrate, to deliver the core azabicyclo[3.3.0]octadiene substructure. Subsequent manipulation of the peripheral functionality then delivered (+/-)-meloscine.
Synthesis studies on the Melodinus alkaloid meloscine
作者:Ken S. Feldman、Joshua F. Antoline
DOI:10.1016/j.tet.2012.12.032
日期:2013.2
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
Allenyl Azide Cycloaddition Chemistry: Exploration of the Scope and Mechanism of Cyclopentennelated Dihydropyrrole Synthesis through Azatrimethylenemethane Intermediates
作者:Ken S. Feldman、Malliga R. Iyer、Carlos Silva López、Olalla Nieto Faza
DOI:10.1021/jo8008066
日期:2008.7.1
Detailed studies of the thermal conversion of 1-azidohepta-3,4,6-trienes into cyclopentennelated dihydropyrroles are presented. High levels of diastereoselectivity and regioselectivity are documented. A mechanistic proposal that accounts for all of the diverse results is developed through the use of density functional calculations. These calculations provide support for the intervention of unexpected mechanistic subtleties, such as the planarity of an azatrimethylenemethane diyl intermediate and an apparent Woodward-Hoffmann-type electrocyclization of a five-atom diyl array.