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

• Published in: Bioscience, biotechnology, and biochemistry Vol. 64; no. 2; pp. 341 - 347
• Main Authors: SHIRAIWA, Tadashi, TADOKORO, Kohya, ISHIKAWA, Joji, TANAKA, Haruyuki, MASAKI, Tooru, KUROKAWA, Hidemoto
• Format: Journal Article
• Language: English
• Published: England Japan Society for Bioscience, Biotechnology, and Agrochemistry 01.02.2000; Oxford University Press
• Subjects: 1,4-thiazane-3-carboxylic acid; 1,4-thiazane-3-carboxylic acid 1-oxide; asymmetric transformation; Crystallization; Magnetic Resonance Spectroscopy; Molecular Structure; Pipecolic Acids - chemical synthesis; Stereoisomerism; tartaric acid
• DOI: 10.1271/bbb.64.341
• ISSN: 0916-8451

In order to synthesize four stereoisomers of 1,4-thiazane-3-carboxylic acid 1-oxide (TCA*SO), (S)-1,4-thiazane-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°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.