PURPOSE: To prepare a penicillanic acid derivative or its salt useful as an antibacterial agent, by eliminating the protecting group from a specific protected penicillanic acid derivative.
CONSTITUTION: A compound of formula II (R1 is H or lower alkyl; R2 is H or OH; R3 are 2W3 OH groups, at least two of which are adjacent) is obtained by eliminating the protecting group of a compound of formula I (R21 is H or OH which may be protected; R31 are R3 or protected R3; Y is H or carboxy-protecting group; at least one of R21, R31 and Y is protecting group). The protecting group of R21 and R31 is e.g. lower alkanoyl group, which can be eliminated by treating with a base in a solvent in the presence of an alcohol, etc. The protecting group of Y is e.g. trimetylsilyl group, which can be eliminated by treating with water or an alcohol.
Next Patent: PREPARATION OF BENZYLPENICILLIN DERIVATIVE OR ITS SALT