Dipolar cycloaddition of novel 6-(nitrileoxidomethyl) penam sulfone: an efficient route to a new class of beta-lactamase inhibitors.

6-(Nitrileoxidomethyl) penam sulfone intermediate was prepared in a few steps starting from commercially available (+)-6-aminopenicillanic acid. This intermediate underwent smooth 1, 3-dipolar cycloaddition reactions with various alkenes and alkynes to give cycloadducts in moderate to good yields. By this new method, several potent beta-lactamase inhibitors were synthesized. The regio- and stereoselectivity outcomes of the cycloaddition process are also discussed.