A compound of the formula wherein: R1, R2, R3, R4, R5, R6 are as defined herein, useful for the inhibition of inhibition of matrix metalloproteases (MMPs)and for treating conditions mediated by elevated levels of MMPs such as osteoarthritis, rheumatoid arthritis, septic arthritis, periodontal disease, gingivitis, solid tumor growth and tumor invasion by secondary metastasis, corneal ulceration, dermal ulceration, epidermolysis bullosa, neural degeneration, multiple sclerosis and surgical wound healing.