The present invention provides compounds of the formula I: its enantiomers, diastereomers, racemic mixtures thereof, prodrugs, crystalline forms, non-crystalline forms, amorphous forms thereof, solvates thereof, metabolites thereof, and pharmaceutically acceptable salts, wherein the ring A substituent groups are fully defined in the following disclosure. The compounds of formula I are inhibitors of metalloproteases such as matrix metalloproteases and sheddases, and are useful in treating diseases such as rheumatoid arthritis, psoriasis, neoplastic diseases, allergies and all those diseases wherein inhibition of MMPs is desirable.