Shiratori Pharmaceutical Co., Ltd.

Daiichi Sankyo Company, Limited

Asubio Pharma Co. Ltd.

Shinnosuke Tazawa

Katsumi Hotoda

Hiroomi Kiyono

A method for selectively producing stable alpha form crystals of sapropterin hydrochloride is provided. In this method, the alpha form crystal of sapropterin hydrochloride is produced by dissolving sapropterin hydrochloride with hydrochloric acid at a concentration of not less than 4 mol/L at not less than 70 degrees C.; adding heated ethanol to the solution; and cooling the solution at a cooling rate of not faster than 3 degrees C./min to a temperature of 40 to 55 degrees C. to precipitate the crystals.

Method for producing alpha form crystals of sapropterin hydrochloride

To provide a method for producing L-biopterin on a large industrial scale by using a reagent which is inexpensive and easy to handle, without requiring a use of any particular equipment or plants. A method for porducing a biopterin derivative represented by the formula (6): wherein Rand R, which are the same or different from each other, each represents a hydrogen atom, an alkyl group, or an aryl group, comprising: wherein Rand Rare the same as defined above,

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Chiba, Japan

Shinnosuke Tazawa