Scheme 31. Biocatalytic application of strictosidine synthase: (a) chemo-enzymatic synthesis of (+)-nacycline (245), (–)-tetrahydroalstonine (247), and their aza-analogues, and (b) preparation of piperazino[1,2-a]indole alkaloids 250 using indole-1-ethanamine derivatives 249 as substrates.