The invention relates to compound of the formula (I’) or a salt thereof, wherein the substituents are as defined in the specification; to its preparation, to its use as medicament and to medicaments comprising it.本發明係關於式(I’)之化合物或其鹽,其中取代基係如在說明書中定義;關於其製備,關於其作為藥物之用途及包括其之藥物。