4‑Benzoylamino-3-hydroxybutyric Acid, Historically First “Anomalous Racemate”: Reinvestigation

Chiral
4-benzoylamino-3-hydroxybutyric acid (1) was
recognized in 1930 as the first example of “anomalous racemates”
(correct to say, anomalous conglomerates), that is, specific addition
compounds formed by different enantiomers in unequal ratio. Through
the comparative (racemic against homochiral samples) inspection of
the IR spectra, single crystal X-ray diffraction, PXRD analysis, and
solubility data we have found that this substance forms normal racemic
compound in the solid state, and must be excluded from the very short
list of anomalous conglomerates. At the same time homo-1 is dissolved in 25 times better than rac-1, and this feature belongs to another interesting
and rare type, namely, “anticonglomerates”. Some of
the reasons for this behavior are discussed.