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The Polymorphs of L ‐Phenylalanine
Author(s) -
Ihlefeldt Franziska Stefanie,
Pettersen Fredrik Bjarte,
von Bonin Aidan,
Zawadzka Malgorzata,
Görbitz Carl Henrik
Publication year - 2014
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201406886
Subject(s) - phenylalanine , amino acid , chemistry , molecule , crystal structure , crystallography , acetic acid , stereochemistry , organic chemistry , biochemistry
The solid‐state structure of the amino acid phenylalanine (Phe) offers a potential key to understanding the behavior of a large class of important aromatic compounds. Obtaining good single crystals is, however, notoriously difficult. The structure of the common polymorph of Phe, form I, was first reported by Weissbuch et al. (as D ‐Phe) in 1990, but the correctness of the published C 2 unit cell with two disordered molecules in the asymmetric unit was later questioned and other space groups suggested. The identity of form I of L ‐Phe is here established to be P 2 1 with Z ′=4, based on data from a well‐diffracting single crystal grown from an acetic acid solution of the amino acid. A second new polymorph, form IV, together with the two recently described forms II and III provide unprecedented information on the structural complexity of this essential amino acid. It is furthermore documented that the racemate, dl ‐Phe, does not grow proper single crystals.