The Chemical Shift of the Alpha Carbon in Amino‐Acids as a Parameter for QSAR Studies of Oligopeptides

The 13 C‐NMR chemical shift δH of the α‐carbon in amino‐acids is proposed as a new parameter for QSAR studies of biologically active oligopeptides. δH which is known for common amino‐acids, is mainly a measure of the electronic shielding of the α‐carbon. In the aliphatic series, it is computable by empirical rules and very sensitive to β‐branching. In this study, δH is shown to describe accurately as a single continuous parameter the variations of the biological activity of angiotensin II, when the residue in its position 5 is varied.