An unusual kinetic approach to the Pictet–Spengler reaction was investigated, in which l - or d -tryptophan methyl ester reacted with aldehydes of 1,2- O -cyclohexylidene-3-allyloxy-α- d -xylofuranose, yielding exclusively the cis or trans diastereomer of tetrahydro-β-carboline glycoside, respectively, with complete stereocontrol.