- 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
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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.
- Shiraiwa, Tadashi,Tadokoro, Kohya,Ishikawa, Joji,Tanaka, Haruyuki,Masaki, Tooru,Kurokawa, Hidemoto
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p. 341 - 347
(2007/10/03)
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- Synthesis of Optically Active 1,4-Thiazane-3-carboxylic Acid via Optical Resolution by Preferential Crystallization of (RS)2-Amino-3-[(2-chloroethyl)sulfanyl]propanoic Acid Hydrochloride
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Optically active 1,4-thiazane-3-carboxylic acid [TCA] was synthesized from cysteine via optical resolution by preferential crystallization. The intermediate (RS)-2-amino-3-[(2-chloroethyl)sulfanyl]propanoic acid hydrochloride [(RS)-ACS-HCl] was found to exist as a conglomerate based on its melting point, solubility and IR spectrum. (RS)-ACS·HCl was optically resolved by preferential crystallization to yield (R)- and (S)-ACS·HCl. (R)- and (S)-ACS·HCl thus obtained were recrystallized from a mixture of hydrochloric acid and 2-propanol, taking account of the solubility of (RS)-ACS·HCl, efficiently yielding both enantiomers in optically pure forms. (R)- and (S)-TCA were then respectively synthesized by the cyclization of (R)- and (S)-ACS·HCI in ethanol in the presence of triethylamine.
- Shiraiwa, Tadashi,Tadokoro, Kohya,Tanaka, Haruyuki,Nanba, Keiichiro,Yokono, Noriyoshi,Shibazaki, Katsuyoshi,Kubo, Motoki,Kurokawa, Hidemoto
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p. 2382 - 2387
(2007/10/03)
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