Asymmetric Total Synthesis of Biphenylquinolizidine Alkaloids 4″-O-Demethyllythridine and 14-epi-4″-O-Demethyllythridine.

The first asymmetric total synthesis of new biphenylquinolizidine alkaloids 4″-O-demethyllythridine and 14-epi-4″-O-demethyllythridine isolated from Heimia salicifolia was accomplished. The key steps in the synthesis were a copper(I)-catalyzed asymmetric intramolecular aza-Michael reaction to build a chiral 4-arylquinolizidine unit and an intramolecular Suzuki-Miyaura cross-coupling reaction to construct a macrolactone ring comprising a biphenyl moiety.

Prolinate Salts as Catalysts for α-Aminoxylation of Aldehyde and Associated Mechanistic Insights.

Potassium and tetrabutylammonium prolinate salts are efficient catalysts in the α-aminoxylation reaction of aldehydes and nitrosobenzene, to afford synthetically useful chiral α-aminoxylated aldehydes in nearly enantiomerically pure form. This is the first reaction in which prolinate is more reactive and enantioselective than proline. Because of its higher reactivity, the catalyst loading can be reduced. A reaction mechanism involving the activation of nitrosobenzene through N-protonation of a hydrogen-bonded water molecule is proposed.