The present invention relates to a novel method of preparing a compound of formula (I) or salt thereof, to novel intermediate compounds, to the use of said novel intermediate compounds for the preparation of said compound of formula (I) or salt thereof. The present invention also relates to crystalline forms, form A, of a compound of formula (I), pharmaceuticals and uses thereof.本發明係關於製備式(I)化合物或其鹽之新穎方法、新穎中間體化合物、該等新穎中間體化合物用於製備該式(I)化合物或其鹽之用途。本發明亦係關於式(I)化合物之結晶形式(即形式A)、其醫藥及用途。