Patent ID: 8389742

Claim:
A process for preparing 2′-(4-bromo-2-fluorobenzyl)spiro[pyrrolidine-3,4′(1′H)-pyrrolo[1,2-a]pyrazine]-1′,2,3′,5(2H′)-tetraone, comprising the following steps: (1) converting a compound of formula (Ia) into a compound of formula (IV): wherein R 1 is a C 1-6 alkyl group; a C 3-8 cycloalkyl group; a benzyl group in which the benzene ring moiety may be optionally substituted by one or two atoms or groups independently selected from the group consisting of a halogen atom, a C 1-4 alkyl group, a C 1-4 alkoxy group, and a cyano group; or an aryl group or a heteroaryl group optionally substituted by one or two groups independently selected from the group consisting of a C 1-4 alkyl group, and a C 1-4 alkoxy group; R 3 is a benzyl group in which the benzene ring moiety may be optionally substituted by one or two atoms or groups independently selected from the group consisting of a halogen atom, a C 1-4 alkyl group, a C 1-4 alkoxy group, a cyano group, and a nitro group, with the proviso that the compound wherein R 1 is a benzyl group in which the benzene ring moiety may be optionally substituted by one or two atoms or groups independently selected from the group consisting of a halogen atom, a C 1-4 alkyl group, a C 1-4 alkoxy group and a cyano group is excluded, or a 2,2,2-trichloroethyl group, by decomposing the compound of formula (Ia) wherein R 3 is a benzyl group in which the benzene ring moiety may be optionally substituted by one or two atoms or groups independently selected from the group consisting of a halogen atom, a C 1-4 alkyl group, a C 1-4 alkoxy group, a cyano group, and a nitro group in a catalytic hydrogenolysis or a catalytic hydrogen transfer, or by reacting the compound of formula (Ia) wherein R 3 is a 2,2,2-trichloroethyl group with zinc; (2) converting an amino group of the compound of formula (IV) of step (1) into a 1-pyrrolyl group; (3) converting the 1-pyrrolyl group of step (2) into a 2-trichloroacetylpyrrol-1-yl group; and (4) reacting a product of step (3) with 4-bromo-2-fluorobenzylamine to convert the product of step (3) into 2′-(4-bromo-2-fluorobenzyl)spiro[pyrrolidine-3,4 ′(1′H)-pyrrolo[1,2-a]pyrazine]-1′2,3′5(2H′)-tetraone.