DFT studies of the ring-opening mechanism of SB-3CT, a potent inhibitor of matrix metalloproteinase 2.

SB-3CT is a 2-[(arylsulfonyl)methyl]thiirane that achieves potent inhibition, by a thiirane-opening mechanism, of the MMP2 and MMP9 zinc metalloproteases. The deprotonation mechanism for thiirane opening of SB-3CT and for the opening of its oxirane analogue, both relevant to the inhibition of MMP2, was investigated computationally using the acetate anion as the Brønsted base and in methanol and acetonitrile as solvents. The activation barriers for the reaction show a significant stereoelectronic effect. The lowest energy paths have the breaking C-H bond gauche to both sulfone oxygens and with this C-H bond anti to the breaking C-S bond of the thiirane. The calculated primary isotope effect agrees with experimental data.