The invention relates to novel processes for preparing penam derivatives, such as Tazobactam and derivatives thereof. The processes according to the invention encompass procedures for the protection and deprotection of the carboxylic group as well as for the oxidation of the sulphur moiety of penam derivatives. Additionally, the present invention relates to new intermediates for the production of penam derivatives, allowing the desired penam-derivatives to be formulated with high purity and in good yields.