PHOTODECARBOXYLATION OF DX-9065A, A NEW FACTOR XA INHIBITOR, IN AQUEOUS-SOLUTION

The photodegradation reaction of inyl]oxy]phenyl]-3-(7-amidino-2-napht hyl)propanoic acid hydrochloride pentahydrate (DX-9065a), a new factor Xa inhibitor, was investigated in aqueous solution at various pH valu es (1.1-8.0) at 25 degrees C. The photodegradation of DX-9065a followe d apparent first-order kinetics under artificial sunlight in a fairly good manner. The photodegradation rates of DX-9065a in a neutral solut ion were higher than those in acidic solution. The log k-pH profile in dicated that the photodegradation rate of DX-9065a was related to the dissociation of the carboxyl group and suggested that the main photo-l abile species was the carboxylate form. Further kinetic study showed t hat the carboxylate form of DX-9065a underwent decarboxylation quantit atively to produce D41-1077, the photodecarboxylation product, on irra diation, while the carboxylic acid form of DX-9065a did not perform an y photodecarboxylation. Moreover, the photodecarboxylation mechanism w as discussed in relation to the kinetics and photodegradation pathway.