Stereoselectivity in the Oligomerization of Racemic Tryptophan N‐Carboxyanhydride (NCA‐Trp) as Determined by Isotope Labeling and Mass Spectrometry

The polycondensation of tryptophan N‐carboxyanhydride (NCA‐Trp) is investigated in the presence and in the absence of POPC (1‐O‐palmitoyl‐2‐O‐oleoyl‐sn‐glycerol‐3‐O‐phosphocholine) liposomes with the aim to study and to quantify possible stereoselective effects of the process. A novel technique, based on isotope labeling of one enantiomer, and high performance liquid chromatography mass spectrometry (LC‐MS) allow determination of the individual stereoisomer distribution of oligomers up to n=10. For the first time, the preferential homochiral growth and the relative stereoisomer distributions for each oligomer length are directly demonstrated.