Total Synthesis of (+)-Isatisine A

Abstract

The asymmetric total synthesis of (+)-isatisine A has been accomplished commencing with a Lewis acid-catalyzed cyclization of homochiral (S)-vinylcyclopropane diester and N-tosylindole-2-carboxaldehyde to construct the tetrahydrofuran ring. A palladium-catalyzed oxidative decarboxylation was utilized to obtain the dihydrofuran required for the subsequent dihydroxylation reaction to install the diol present on the tetrahydrofuran ring. The total synthesis was completed by an indole oxidation and electrophilic aromatic substitution sequence to construct isatisine A acetonide, which was then carried forward to the antipode of the natural product. The absolute configuration of the natural enantiomer (-)-isatisine A was determined to be C2(S), C9(R), C10(S), C12(R), and C13(R).