Preparation of R-(+)-3,4-dimethoxybenzyl, 2-methoxy-1-naphthyl sulfoxide and diastereoselective addition of lithiated anion of this reagent to cyclicnitrone. Asymmetric synthesis of optical pure isoquinoline alkaloids

The addition of the lithium carbanion of (R)-(+)-3,4-dimethoxybenzyl 2-meth oxy-1-naphthyl sulfoxide 3 to cyclic nitrone 4, under kinetically controlle d conditions gave isoquinoline sulfoxide derivatives 5 and 6 in high diaste reoselectivities, Under equilibrium controlled conditions poor diastereosel ectivity results. The chiral (R)-(+)-3,4-dimethoxybenzyl 2-methoxy-1-naphth yl sulfoxide 3 was easily prepared by the reaction of 3,4-dimethoxybenzylma gnesium chloride 2 with (-)-(S) menthyl 2-methoxy-naphthalene sulfinate 1 i n dry benzene. This methodology allows for the synthesis of the isoquinolin e alkaloid (R)-(-)-norlaudanosine 8 in three efficient synthetic steps.