Chiral acetylenic sulfoxide in enantioselective synthesis of tetrahydroisoquinoline and tetrahydro-β-carboline alkaloids. Total synthesis of (R)-(+)-Carnegine and (R)-(+)-tetrahydroharman

Michael addition of 2-(3,4-dimethoxyphenyl)ethylamine 3 or tryptamine 4 onto chiral acetylenic sulfoxides 2 followed by acid induced cyclization afforded the basic alkaloid skeleton of tetraisoquinoline and tetrahydro-β-carboline in high to moderate diastereoselectivity. Optically pure (R)(+)-Carnegine and (R)-(+)-tetrahydroharman have been synthesized.