Chiroptical Properties of the Guanidine Chromophore

The CD spectra of 15 alfa-guanidino-acids, derived from 15 proteinaceous amino acids were measured and analysed. Using L-amidino-proline, L-amidino-prolinol, and L-amidino- 4-hydroxyproline as standards the sector rule for prediction of the sign of the Cotton effect at 190-195 nm, attributed to the guanidine chromophore, was constructed. X-ray analysis of crystal structures of L-amidino-4-hydroxyproline and L-amidinomethionine was also performed.