A novel series of sulfone N-formylhydroxylamines (retrohydroxamates) have been investigated as matrix metalloproteinases (MMP) inhibitors. The substitution of the ether linkage of ABT-770 (5) with a sulfone group 13a led to a substantial increase in activity against MMP-9 but was accompanied by a loss of selectivity for inhibition of MMP-2 and-9 over MMP-1 and diminished oral exposure. Replacement of the biphenyl P1'substituent ...