The present invention relates to the compounds of formula (I), are cystatins, including but unlimited what cathepsin K, L, S and B inhibitor. The treatment of these compound whats wherein shows that the disease of bone resorption, such as osteoporosis need to be inhibited.本發明涉及式(I)的化合物,其是半胱氨酸蛋白酶抑制劑,包括但不限於組織蛋白酶K、L、S和B的抑制劑。這些化合物用於治療其中表明需抑制骨吸收的疾病,例如骨質疏鬆症。