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AssigneeTanabe Seiyaku Co., Ltd.
InventorsIchiro Chibata, Shigeki Yamada, Masao Yamamoto, Hisato Sanematsu
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Seed crystals of one optically active enantiomer of 6-chlorotryptophan methanesulfonate or 6-chlorotryptophan benzenesulfonate are added to a supersaturated solution of DL-6-chlorotryptophan methanesulfonate or DL-6-chlorotryptophan benzenesulfonate. Crystallization of the optically active enantiomer results. The crystals are recovered. Alternatively, crystals of the optically active enantiomer may be added to a hot solution of DL-6-chlorotryptophan methanesulfonate or DL-6-chlorotryptophan benzenesulfonate to produce a supersaturated solution. The solution is then cooled to crystallize out the optically active enantiomer. Optically active 6-chlorotryptophan is prepared by treating optically active 6-chlorotryptophan methanesulfonate or 6-chlorotryptophan benzenesulfonate with an alkaline agent or an ion exchange resin.
A process for resolving DL-6-chlorotryptophan methanesulfonate into its optically active enantiomers, which comprises the steps of adding a first enantiomer to a solution of DL-6-chlorotryptophan methanesulfonate, whereby a first supersaturated solution with respect to DL-6-chlorotryptophan methanesulfonate is formed, to initiate crystallization of said first enantiomer from said first supersaturated solution, and recovering the crystallized first enantiomer.
A process for preparing optically active 6-chlorotryptophan which comprises the steps of supersaturating an aqueous solution of DL-6-chlorotryptophan methanesulfonate, adding crystals of a first optically active enantiomer of 6-chlorotryptophan methanesulfonate to said supersaturated solution, crystallizing said first optically active enantiomer from said supersaturated solution, recovering said first crystallized optically active enantiomer, and then treating said recovered first optically active enantiomer with an alkaline agent or an ion-exchange resin.
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