Patent ID: 8288553

Claim:
A method for preparing the compound of formula (I) wherein P 1 and P 2 represent groups protecting the carboxylic acid and oxyamine functions, comprising a beta-ketosulfoxonium compound of formula: wherein P 1 is as defined here above and P 3 represents an amine protecting group, is treated with a reagent generating HCl, in order to obtain the compound of formula: wherein P 1 and P 2 are as defined here above, which is treated without isolating it, with hydroxylamine derivative, in order to obtain the compound of formula: wherein P 1 and P 3 are as defined here above and P 2 represents a protecting group of the oxime, the amine of which is de-protected by the action of an acid, in order to obtain the compound of formula: wherein P 1 and P 2 are defined as here above, which is cyclized by the action of a base, in order to obtain the compound of formula: wherein P 1 and P 2 are defined as here above, the oxime function of which is reduced by the action of a reducing agent, in order to obtain the expected compound of formula (I) which, if desired, is salified by the action of an acid.