A METHOD OF PREPARING A 4-OXO-1- (3 SUBSTITUTED PHENYL) -1, 4-DIHYDRO-1, 8-NAPHTHYRIDINE-3- CARBOXAMIDE PHOSPHODIESTERASE-4 INHIBITOR

摘要

The invention is directed tc methods of preparing a compound of the structural formula (22) crystal form of structural formulae (21) and its free acid.