| abstract |
ABSTRACT OF THE DISCLOSURE This invention relates to the phthalide ester of 6-[b(-).alpha.-aminophenylacetamido] penicillanic acid and its pharmaceutically acceptable acid addition salts, and to a process for its preparation. The esters of the invention are novel and are useful in that they produce high serum concentrations of the parent penicillin when ad-ministered orally, and higher than can be achieved with the parent penicillin itself. The esters of the present invention may be pre-pared by a process which comprises reacting 6-aminopenicillanic acid phthalide ester or a silyl derivative thereof with a reactive N-acylating derîvatîve of the (D) isomer of a compound of the formula: wherein X is an amino group, a protected amino group or a group which is convertible to an amino group, removing the silyl group, if present, by hydrolysis or alcoholysis, and if X is not an amino group, converting it to such a group under neutral or acid conditions. |