Synthesis of 3-benzylidene-dihydrofurochromen-2-ones: promising intermediates for biflavonoid synthesis.
A route to 3-benzylidene dihydrofurochromen-2-ones from 2H-chromenes is described. Lactonization of 2H-chromenes was achieved using a two-step cyclopropanation-rearrangement sequence. Subsequent conversion of these intermediates to the corresponding α-benzylidene lactones was achieved by lithium enolate Aldol reaction, followed by base-promoted elimination of the aldolate mesylates. The alkene geometry was found to be base-dependent. While KOtBu favored formation of theE-isomer, DBU showed a slight preference for theZ-isomer. In further studies, these 3-benzylidene dihydrofurochromen-2-ones were converted to polyaromatic structures possessing all the required functionality for biflavonoid synthesis.
Department of Chemistry, Mississippi State University, Mississippi State, Mississippi 39762, USA.
Verna
V
Baron
Department of Chemistry, Mississippi State University, Mississippi State, Mississippi 39762, USA.
Keith T
KT
Mead
biflavonoids; chamaejasmine; donor-acceptor cyclopropanes; isochamaejasmine; α-benzylidene lactones