Some α-amino acids(I)(L-tryptophan and L-Dopa) were subjected to the Pictet-Spengler reaction with aldehydes(II) according to the biosynthetic route. From the resultant condensation products (III) was eliminated the C_1-unit derived from the α-amino acids to give optically active compounds(IV). Using this biogenetically patterned 1,3-transfer of asymmetry, S(-)-tetrahydroharman(XVIIb) and S(-)-1,2,3,4,6,7,12,12b-octahydroindolo[2,3-a]quinolizine(XX) were synthesized from L-tryptophan. S(+)-Laudanosine(XXVIa) was also prepared from L-Dopa. The key steps of the 1,3-transfer of asymmetry are the Pictet-Spengler reaction, α-aminonitrile formation, followed by the reductive decyanization with sodium borohydride. Results of model reactions for the reductive decyanization are shown in the Table.
