Patent ID: 7960546

Claim:
A process for preparing a compound of formula (I) wherein R a denotes a benzyl, 1-phenylethyl or 3-chloro-4-fluorophenyl group, R b denotes a methyl, ethyl, isopropyl, cyclopropyl, 2-methoxyethyl, tetrahydrofuran-3-yl, tetrahydrofuran-2-yl-methyl, tetrahydrofuran-3-yl-methyl, tetrahydropyran-4-yl or tetrahydropyran-4-yl-methyl group, R c denotes a methyl, ethyl or 2-methoxyethyl group or R b and R c together with the nitrogen atom to which these groups are bound denotes a morpholino or homomorpholino group optionally substituted by one or two C 1-3 -alkyl groups and R d denotes a cyclopropylmethyl, cyclobutyl, cyclopentyl, tetrahydrofuran-3-yl, tetrahydrofuran-2-yl-methyl, tetrahydrofuran-3-yl-methyl, tetrahydropyran-4-yl or tetrahydropyran-4-yl-methyl group, by f) reacting a phosphonic ester of formula wherein R a denotes a benzyl, 1-phenylethyl or 3-chloro-4-fluorophenyl group, R d denotes a cyclopropylmethyl, cyclobutyl, cyclopentyl, tetrahydrofuran-3-yl, tetrahydrofuran-2-yl-methyl, tetrahydrofuran-3-yl-methyl, tetrahydropyran-4-yl or tetrahydropyran-4-yl-methyl group and R 1 and R 2 each independently of one another denote a C 1-4 -alkyl group, with the hydrogen sulphite adduct of formula wherein M + denotes a cation, R b denotes a methyl, ethyl, isopropyl, cyclopropyl, 2-methoxyethyl, tetrahydrofuran-3-yl, tetrahydrofuran-2-yl-methyl, tetrahydrofuran-3-yl-methyl, tetrahydropyran-4-yl or tetrahydropyran-4-yl-methyl group, R c denotes a methyl, ethyl or 2-methoxyethyl group or R b and R c together with the nitrogen atom to which these groups are bound denote a morpholino or homomorpholino group optionally substituted by one or two C 1-3 -alkyl groups.