Patent ID: 8030486

Claim:
A process for preparing (3R)-2′-(4-bromo-2-fluorobenzyl)spiro[pyrrolidin-3,4′(1′H)-pyrrolo[1,2-a]pyrazin]-1′,2,3′,5(2′H)-tetraone comprising the following steps: 1) a step in which a compound of the formula (2): wherein R′ is a) an amino group having a protecting group which can be removed by hydrogenolysis or b) a tert-butoxycarbonylamino group, and R 2 is an ethyl group optionally substituted with one or two methyl group(s) at α-position, provided that R 2 is not a tert-butyl group when R′ is a tert-butoxycarbonylamino group, is reacted with a base to prepare a succinimide derivative of the formula (3): wherein R′ is a) an amino group having a protecting group which can be removed by hydrogenolysis or b) a tert-butoxycarbonylamino group, and R 2 is an ethyl group optionally substituted with one or two methyl group(s) at α-position, provided that R 2 is not a tert-butyl group when R 1 is a tert-butoxycarbonylamino group; 2) a step of converting R 1 (an amino group having a protecting group which can be removed by hydrogenolysis or a tert-butoxycarbonylamino group) of the succinimide derivative (3) into an amino group; 3) a step of converting the amino group of the product resulting from the above step 2) into a pyrrol-1-yl group; 4) a step of converting the pyrrol-1-yl group of the product resulting from the above step 3) into a 2-trichloroacetylpyrrol-1-yl group; and (5) a step of preparing (3R)-2′-(4-bromo-2-fluorobenzyl)spiro[pyrrolidin-3,4′ (1′H)-pyrrolo[1,2-a]pyrazin]-1′,2,3′,5(2′H)-tetraone by reacting the product resulting from the above step 4) with 4-bromo-2-fluorobenzylamine.