As a result, LC-MS analysis of the derivatives showed the same retention time as those prepared from a sample of authentic standards previously reported in the literature as D-tyrosine, N-methyl-L-phenylalanine, and D-serine. A D-configuration of N-methyl-2-chloro-3-hydroxy-4-methoxy-phenylalanine residue was established by measuring its specific optical rotation ([α]D 25 0.0928, c 0.023, MeOH) after purification from acid hydrolysis. This confirmed the absolute configurations of pepticinnamin E. Based on the common biosynthetic pathway, the absolute configurations of 2-4 were established as the same as those of pepticinnamin E. Indeed, they have exhibited similarities in the ECD spectra (Figure ). Figure . HPLC analysis of the hydrolysates of pepticinnamin E in comparison with standards.