Access to Guaianolides:Highly Efficient Stereocontrolled Total Synthesis of (+-)-Geigerin

摘要

Guaianolides,which possess a bicyclo[5.3.0]decane skeleton,represent one of the largest groups of naturally occurring sesquiterpene lactones.They exist in two forms,guaian-6,12-olides and guaian-8,12-olides (Scheme 1),and show important,diverse biological activities.Geigerin (1,Scheme 1),a member of the guaian-8,12-olide class,was initially isolated in 1936 from G.aspera Harv.,a South African species of Geigeria,known colloquially as the vermeerbos ("vomiting bush").