A triple diene-transmissive Diels-Alder strategy to build the quassinoid framework.
[chemical reaction: see text]. An advanced intermediate to the highly oxygenated triterpene quassinoids was prepared in 14 steps from tetrahydrofuran. The key steps are three diene-transmissive Diels-Alder cycloadditions. Several features of this synthesis are noteworthy, including a successful Mitsunobu reaction on an allenylic alcohol, a rare [4 + 2] cycloaddition involving an enethiol ether dienophile, and complete control over all 10 chiral centers created.
Dion
Amélie
A
Département de Chimie, Université de Sherbrooke, 2500 Boul. Université, Sherbrooke, QC, Canada J1K 2R1.
Dubé
Pascal
P
Spino
Claude
C
D003500:Cyclization; D005663:Furans / Q000138:chemical synthesis / Q000737:chemistry*; D015394:Molecular Structure; D010084:Oxidation-Reduction; D036702:Quassins / Q000138:chemical synthesis* / Q000737:chemistry*
D005663:Furans; D036702:Quassins