Abstract: In a process for the preparation of 6,6-dibromo-penicillanic acid-1,1-dioxide comprising reacting 6.beta.-amino-penicillanic acid-1,1-dioxide with a nitrosating agent in the presence of bromine and an inorganic acid or strong organic acid, the improvement comprising effecting the reaction in the presence of an alcohol resulting in a high purity product.

Abstract: A novel process for the preparation of high purity penicillanic acid-1,1-dioxide comprising subjecting 6,6-dibromo-penicillanic acid-1,1-dioxide to dehalogenation with magnesium in association with an acid in high yields.

Abstract: A process for the preparation of penicillanic acid-1,1-dioxides of the formula ##STR1## wherein X is selected from the group consisting of hydrogen and substituent such as halogen or acetoxy and R is selected from the group consisting of hydrogen, a pharmaceutically acceptable metal ion and/or ester radical comprising debrominating a 6-.alpha.-bromo- and/or 6,6-dibromo-penicillanic 1,1-dioxide selected from the group consisting of the formula ##STR2## wherein X and R have the above definition in an aqueous containing medium with zinc in association with an acid having a pK.sub.a -value measured in water less than 3.5 and optionally if R is H converting the acid into a pharmaceutically acceptable salt or ester.