4-Hydroxy-2-thiazolines were prepared by interrupting the Hantsch thiazole synthesis at the stage of cyclization. The chemical behavior of the tertiary amines, as well as the AB-quartet pattern at around 3.5 ppm in the NMR spectra, supported the cyclic structure (VII). Thioliminoester structure (VIIIa) proposed by M. Steude was unambiguously denied by the present paper.
