Patent ID: 9272992
Filing Date: 2016-03-01
CPC Classification: A61P,C07B,C07C

Claim Text:
1. A method for preparing a compound of the general formula (I), wherein X is 2.0 or 3.0, comprising the steps of: suspending (1S,2S,3S,4R)-3-[(1S)-1-acetylamino-2-ethyl-butyl]-4-guanidino-2-hydroxy-cyclopentyl-1-carboxylic acid crude product in water and dissolving by heating to 50-90° C. to afford a first solution; allowing the first solution to stand for a moment and then adding activated carbon to the first solution; refluxing the first solution by heating for 10 minutes and filtering while the first solution is hot to remove the activated carbon; cooling the first solution to 35-75° C. and then adding an organic solvent to the first solution to afford a second solution; adding a crystal seed of the compound of the general formula (I) to the second solution; placing the second solution in a sealed vessel, allowing the second solution to stand, and cooling the second solution at a suitable cooling rate to precipitate the compound of the general formula (I) as a crystal product, and then filtering and collecting the compound of the general formula (I).