Hydrogen bonding pattern in N-benzoyl(-dl-)-l-phenylalanines as revealed by solid-state NMR spectroscopy

The nature of the hydrogen bonding pattern has been investigated in N-benzoyl-dl-phenylalanine (1) and N-benzoyl-l-phenylalanine (2) polymorphes by solid-state NMR spectroscopy. It has been shown that the multiple resonances of carboxyl carbon in 2 are directly connected to different types of hydrogen bonding. The differences in intermolecular distances of carboxyl groups involved in different types of hydrogen bonding have been visualized by the 2D exchange and 1D ODESSA experiments. Potential applications of such a new approach include the exploration of intermolecular distances in hydrogen bonded compounds with singly labeled biomolecules.