Process and intermediate compounds to prepare integrase inhibitors

A method of preparing a compound of formula ** Formula ** or a salt thereof, wherein a compound of formula ** Formula ** or a salt thereof is prepared and converted to a compound of formula 10, characterized by that the compound of formula 4 is prepared from a compound of formula ** Formula ** or a salt thereof, by the steps of replacing the bromine atom with a carboxyl group in a carboxylation reaction to provide the compound of formula ** Formula ** or a salt thereof and replacing the hydroxyl group in compound 3 with a hydrogen atom to provide the compound of formula 4.