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

Abstract

Chiral 4-benzoylamino-3-hydroxybutyric acid (<b>1</b>) 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 <i>homo</i>-<b>1</b> is dissolved in 25 times better than <i>rac</i>-<b>1</b>, and this feature belongs to another interesting and rare type, namely, “anticonglomerates”. Some of the reasons for this behavior are discussed