U.S. Pat. No. 4,244,951 discloses a series of 6'-acylaminopenicillanoyloxymethyl penicillanate 1,1-dioxides of the formula I: ##STR1## wherein R.sup.1 represents certain acyl groups, said compounds of formula I being of value as antibacterial agents.
One method disclosed in U.S. Pat. No. 4,244,951 for the preparation of said antibacterial agents of formula I comprises acylation of the corresponding compound of formula I, wherein R.sup.1 is hydrogen (6'-aminopenicillanoyloxymethyl penicillanate 1,1-dioxide). In turn, it is disclosed that 6'-aminopenicillanoyloxymethyl penicillanate 1,1-dioxide can be prepared by coupling a salt of a 6-(protected-amino)penicillanic acid compound of the formula ##STR2## wherein Z is an amino protecting group and M is a carboxylate salt forming cation, with a compound of the formula ##STR3## wherein X is a good leaving group, followed by removal of the protecting group. Groups which are disclosed as being useful for the group Z are the benzyloxycarbonyl group, the 4-nitrobenzyloxycarbonyl group and the 2,2,2-trichloroethoxycarbonyl group.
However, it has now been discovered that the aforesaid process for the preparation of the compound of the formula I, wherein R.sup.1 is hydrogen, can be improved by using certain alternate groups for protection of the 6-amino group in the 6-aminopenicillanic acid, i.e. the group Z. Specifically, said process for the preparation of the compound of formula I, wherein R.sup.1 is hydrogen, can be improved by using for Z certain groups obtained by reacting 6-aminopenicillanic acid with certain beta-dicarbonyl compounds.
Accordingly, it is an object of this invention to provide an improved process for the preparation of the compound of the formula I, wherein R.sup.1 is hydrogen, which uses certain alternate protecting groups.