Crystalline form of sofpironium bromide and preparation method thereof

Sofpironium bromide crystal Form B characterized by showing peaks at 5.9±0.2, 7.2±0.2, 7.7±0.2, 11.1±0.2, 22.3±0.2, and 24.6±0.2 as diffraction angles 2θ in a powder X-ray diffraction spectrum, wherein Form B is a mixture of

• a) sofpironium bromide cocrystal Form CO, and
• b) sofpironium bromide crystal Form MN,
• wherein said cocrystal Form CO comprises, in a 1:3 ratio:
• a compound shown as formula I-a
• and
• a compound shown as formula I-b
• wherein the cocrystal Form CO has a purity of not less than 98% w/w based on the content of the compound (I), represented by the formula (I)
• said cocrystal Form CO being characterized by showing peaks at 5.9±0.2, 7.6±0.2, 11.0±0.2, and 22.2±0.2 degrees as diffraction angles 2θ in a powder X-ray diffraction spectrum and has a single sharp endothermic peak value of 150° C. using a thermal analysis method as described in Japanese Pharmacopoeia (17th Edition);
• and
• wherein said sofpironium bromide crystal Form MN, which is a single crystal form of formula I-a, is characterized by showing peaks at 7.1±0.1, 21.4±0.1, 22.3±0.1, and 24.5±0.1 as diffraction angles 2θ in a powder X-ray diffraction spectrum.