Crystalline 3',5'-cyclic diguanylic acid

Abstract

A crystal of free acid of 3′,5′-cyclic diguanylic acid containing no metal salt with cobalt, magnesium or the like is provided. A method is sought for obtaining said crystal in a large amount and with ease. By a manufacturing method comprising a step of adding acid to an aqueous solution of 3′,5′-cyclic diguanylic acid so as to lower pH to 1 to 3, crystals of 3′,5′-cyclic diguanylic acid can be obtained in a large amount with ease. Said crystals are free acid crystals which do not contain a metal salt with cobalt, magnesium or the like.

1 . A crystal of 3′,5′-cyclic diguanylic acid. 
     
     
         2 . A crystal of  claim 1  having purity of 97% or more as measured by high-performance liquid chromatography. 
     
     
         3 . A crystal of  claim 1  having purity of 99% or more as measured by high-performance liquid chromatography. 
     
     
         4 . A crystal of  claim 1 , wherein approximately 4 to 6 molecules of water bond or attach to one molecule of 3′,5′-cyclic diguanylic acid. 
     
     
         5 . A crystal of  claim 1 , wherein an endothermic peak is observed at 213 to 217° C. as measured by a thermogravimetric measurement/differential thermal analysis (TG/DTA) apparatus. 
     
     
         6 . A crystal of  claim 1 , wherein characteristic peaks are observed around 3163, 1712, 1637, 1601, 1530, 1470, 1386 and 1339 (cm −1 ) when an infrared absorption spectrum is measured. 
     
     
         7 . A crystal of  claim 1 , wherein characteristic peaks are observed around 8.1, 8.3, 10.8, 11.8, 16.9, 19.1, 19.5, 22.4, 25.0, 26.7, 27.0 and 27.7(°) in diffraction angle (2θ) in X-ray powder analysis. 
     
     
         8 . A manufacturing method of a crystal of 3′,5′-cyclic diguanylic acid comprising a step of adding acid to an aqueous solution of 3′,5′-cyclic diguanylic acid so as to lower pH to 1 to 3. 
     
     
         9 . A manufacturing method of a crystal of 3′,5′-cyclic diguanylic acid comprising the following steps (1) to (3):
 (1) a step of heating an aqueous solution of 3′,5′-cyclic diguanylic acid to 50 to 70° C., 
 (2) a step of adding acid to the solution of 3′,5′-cyclic diguanylic acid so as to lower pH to 1 to 3, and 
 (3) a step of cooling the solution of 3′,5′-cyclic diguanylic acid until it reaches 1 to 10° C.