Abstract
13C‐nmr chemical shifts of backbone carbonyl and side‐chain β‐carbons in polypeptides provide structural information. Recent utilization of substituent effects on 13C‐nmr chemical shifts (principally γ‐effects) has permitted the rationalization of their sequence and conformation dependence when observed in linear, flexible polypeptides. In this report, we apply the γ‐effect method to study the 13C‐nmr chemical shifts observed in solution and in the solid state for the backbone carbonyl and side‐chain β‐carbons in conformationally rigid polypeptides, which are usually cyclic. As found previously for flexible, linear polypetides, the relative 13C‐nmr chemical shifts observed for the backbone carbonyl and side‐chain β‐carbons in conformationally rigid polypeptides are predictable from knowledge of their peptide residue sequence (primary structure) and conformation (secondary structure) via the γ‐effect method.

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