This invention relates to novel processes for preparing compounds of formula (I), wherein R1H is as defined below, which is a salt of the naphthyridone antibiotic 7-(1α,5α,6α)-(6-amino-3-azabicyclo[3.1.0]hex-3-yl)-1-(2,4-difluorophenyl)-6-fluoro-1,4-dihydro-4-oxo-1,8-naphthyridine-3-carbocylic acid and a pharmaceutically acceptable acid. The salt and antibiotics have antibacterial activity. This invention also relates to novel intermediates, and processes for their preparation, of formulae (IV), (IIIB) or (IIIA). The compounds of formulae (IIIA), (IIIB) and (IV) are useful as intermediates in the syntheses of the azabicyclo naphthyridone carboxylic acid alkanesulfonic acid salts of formula (I).