Suzuki-Miyaura cross-coupling of 3-pyridyl triflates with 1-alkenyl-2-pinacol boronates

Enantioselective Synthesis of the Guaipyridine Alkaloid (+)- and (-)-Cananodine

Synthesis of both enantiomers of guaipyridine alkaloid cananodine was achieved. The stereocenter at C8 was set through an Evans alkylation, and the seven-membered carbocycle was constructed using an intramolecular Mizoroki-Heck reaction. Hydrogenation of an exomethylene set the C5 stereocenter. The optical rotation of each enantiomer matched the literature. The synthetic scheme is amenable to analogue preparation. (+)- and (-)-Rupestine G were also prepared.

De Novo Synthesis of Polysubstituted 3-Hydroxypyridines Via “Anti-Wacker”-Type Cyclization

We report an efficient method to prepare polysubstituted 3-hydroxypyridines from amino acids, propargyl alcohols, and arylboronic acids. The process involves Pd(0)-catalyzed anti-selective arylative cyclizations of N-propargyl-N-tosyl-aminoaldehydes with arylboronic acids (“anti-Wacker”-type cyclization), oxidation of the resulting 5-substituted-3-hydroxy-1,2,3,6-tetrahydropyridines to 3-oxo derivatives, and elimination of p-toluenesulfinic acid. This method provides diverse polysubstituted 3-hydroxypyridines, whose hydroxy group can be further substituted by a cross-coupling reaction via a triflate.

Synthesis of cananodine by intramolecular epoxide opening

Cananodine is a guaipyridine alkaloid with activity against liver cancer. Cananodine was synthesized using a remarkable intramolecular opening of a trisubstituted epoxide as the key step in construction of the seven-membered carbocycle of the target. The epoxide opening strategy allows all four stereoisomers of cananodine to be prepared.