title: Synthesis of four stereoisomers of 1,4-thiazane-3-carboxylic acid 1-oxide via the asymmetric transformation (combined isomerization-preferential crystallization) of 1,4-thiazane-3-carboxylic acid.
abstract: In order to synthesize four stereoisomers of 1,4-thiazane-3-carboxylic acid 1-oxide (TCA SO), (S)-1,4thiazane-3-carboxylic acid [(S)-TCA], which is one of the precursors, was prepared by the asymmetric transformation (combined isomerization-preferential crystallization) of (RS)-TCA. This asymmetric transformation was used (2R, 3R)-tartaric acid [(R)-TA] as a resolving agent and salicylaldehyde as the epimerization catalyst in propanoic acid at 110 degrees C to afford a salt of (S)-TCA with (R)-TA in 100% de with a yield of over 90%. Optically pure (S)-TCA was obtained by treating the salt with triethylamine in methanol in a yield of over 80%, based on (RS)-TCA as the starting material. In addition, asymmetric transformation of (R)-TCA gave (S)-TCA in a yield of 60-70%. (S)-TCA was oxidized by hydrogen peroxide in dilute hydrochloric acid to selectively crystallize (1S, 3S)-TCA.SO. (1R, 3S)-TCA SO of 70% de from the filtrate was allowed to form a salt with (R)-TA after a treatment with triethylamine to give (1R, 3S)-TCA SO as a single diastereoisomer. (1R, 3R)- and (1S, 3R)-TCA.SO were also prepared by starting from (R)-TCA that had been synthesized from L-cysteine.
authors.affiliation: Chemical Branch, Faculty of Engineering and Kansai University High Technology Research Center, Kansai University, Suita, Osaka, Japan. shiraiwa@ipcku.kansai-u.ac.jp
authors.forename: T
authors.initials: T
authors.lastname: Shiraiwa
authors.forename: K
authors.initials: K
authors.lastname: Tadokoro
authors.forename: J
authors.initials: J
authors.lastname: Ishikawa
authors.forename: H
authors.initials: H
authors.lastname: Tanaka
authors.forename: T
authors.initials: T
authors.lastname: Masaki
authors.forename: H
authors.initials: H
authors.lastname: Kurokawa
mesh_terms: D003460:Crystallization; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D010875:Pipecolic Acids / Q000138:chemical synthesis*; D013237:Stereoisomerism
chemical_list: D010875:Pipecolic Acids