| 摘要 |
Anhydrous crystalline zilpaterol hydrochloride (I), contg. less than 5% of crystals smaller than 15 mu , the rest of the crystals being smaller than 250 mu , is new. Also claimed are (I)-monohydrate and (I)-trihydrate. The claimed prepn. of (I) comprises: (i) forming a super-satd. soln. of (I) in water or in an ethanol/water mixt. at below 50 degrees C; (ii) cooling the soln. to crystallise the monohydrate; (iii) lowering the temp. to below 20 degrees C to crystallise the trihydrate; and (iv) drying to give the desired prod. A variation on the above procedure comprises dissolving (I) in water at below 30 degrees C to give a satd. aq. soln. from which the trihydrate recrystallises spontaneously. Alternatively, a soln. of (I) in a min. amt. of warm water (60-100 degrees C) is poured into a satd. soln. of (I) in a water/alcohol mixt. which has been previously stirred at below 20 degrees C and seeded with trihydrate, to give the trihydrate, which is then dried (all claimed).
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