Atroposelective Total Synthesis of the Fourfold ortho-Substituted Naphthyltetrahydroisoquinoline Biaryl O,N-Dimethylhamatine

Abstract

A stereoselective total synthesis of O,N-dimethylhamatine, an analogue of an axially chiral naphthylisoquinoline natural biaryl product from tropical Ancistrocladus lianas, is reported. The route features a late-stage atropo-diastereoselective biaryl bond formation. Generation of this especially challenging, sterically hindered tetra-ortho-substituted array was achieved by using Nolan's (IPr*NHC)PdCinCl pre-catalyst under mild Negishi coupling conditions. Discussion is offered regarding the selectivity obtained experimentally and predicted from DFT calculations on the key biaryl coupling step that leads to the desired M-diastereomer.

Keywords: Negishi coupling; Pd catalysis; atropisomerism; bifurcation; density functional calculations; ligand design.