Concise Synthesis of the Multiply Oxygenated ABC-Ring System of the Dihydro-β-agarofurans
摘要:
The multiply oxygenated ABC-ring system of the dihydro-beta-agarofurans was synthesized by employing two highly stereoselective reactions. The quinidine-catalyzed Diels-Alder reaction between a chiral dienophile and 3-hydroxy-4-methyl-2-pyrone simultaneously installed the C2-stereogenic center and two contiguous tetrasubstituted carbon centers (C5 and C10) of the A-ring. After 12 additional transformations, the aldol reaction of the resulting spiral AC-ring cyclized the B-ring with stereoselective introduction of the C7- and C8-centers.
The sesquiterpene lactones cover a diverse and pharmacologically important diversity space. In particular, the electrophilic α-exo-methylene-γ-butyrolactone moiety that is preponderant in this natural product family has been shown to readily engage in covalent inhibition via conjugate addition of cysteine residues in target proteins. However, the synthetic accessibility of sesquiterpenes or related