1. Department of Organic Chemistry, University of Debrecen, P.O. Box 20, H‐4010 Debrecen, Hungary;2. Department of Biochemistry, University of Debrecen, 1 Egyetem tér, H‐4032 Debrecen, Hungary;3. Department of Pharmaceutical Chemistry, University of Debrecen, P.O. Box 70, H‐4010 Debrecen, Hungary;4. Department of Chemistry, Laboratory for X‐ray Diffraction, University of Debrecen, P.O. Box 7, H‐4010 Debrecen, Hungary
Abstract:
Under acetylating conditions racemic thioflavanone thiosemicarbazones cyclize into racemic 3‐acetyl‐spiro1,3,4‐thiadiazoline‐2,4′‐thioflavans] and a racemic 3‐acetylspiro1,3,4‐oxadiazoline‐2,4′‐thioflavan] with trans O(1) or S(1) and Ph(2′eq). Hindered rotation of the endocyclic N(3) acetyl group spirothia‐diazolines caused the formation of isomers separable by HPLC. X‐ray diffraction analyses, 1H‐, 13C‐, and 15N NMR measurements as well as MOPAC QM calculations were performed to reveal the structures of these isomers.
