L-glufosinate intermediate and L-glufosinate preparation method

A method for preparing a compound of Chemical Formula 2, the method comprising a step a of preparing a compound of the following Chemical Formula 2 from a compound of the following Chemical Formula 1,

• wherein the step a comprises
• (i) a step b of preparing a compound of the following Chemical Formula 3 by reacting the compound of Chemical Formula 1 with a first base catalyst, or
• (ii) a step b-1 of preparing a compound of the following Chemical Formula 4 by reacting the compound of Chemical Formula 1 with a second acid catalyst,
• where in the above formulas,
• R1 is Ra—(C═O)—, where Ra is a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, a substituted or unsubstituted alkenyl group having 1 to 6 carbon atoms, a substituted or unsubstituted alkynyl group having 1 to 6 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms, a substituted or unsubstituted aryl group having 6 to 20 carbon atoms, or a substituted or unsubstituted heteroaryl group having 2 to 10 carbon atoms,
• R2 is a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, a substituted or unsubstituted alkenyl group having 1 to 6 carbon atoms, a substituted or unsubstituted alkynyl group having 1 to 6 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 20 carbon atoms, a substituted or unsubstituted heteroaryl group having 2 to 10 carbon atoms, or —Si(Rb)(Rc)(Ra), where Rb, Rc and Rd independently of one another are a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms or a substituted or unsubstituted aryl group having 6 to 20 carbon atoms,
• X is halogen, and
• substituents of the alkyl group, alkenyl group, alkynyl group, cycloalkyl group, aryl group, and heteroaryl group independently of one another are at least one selected from halogen, a carboxyl group (—COOH), an amino group (—NH2), a nitro group (—NO2), a cyano group (—CN), an alkyl group having 1 to 6 carbon atoms, an aryl group having 6 to 10 carbon atoms, and a cycloalkyl group having 3 to 10 carbon atoms.