Novel prostaglandin dehydrogenase inhibiting agents having the structural formula ##STR1## M is H or a pharmaceutically acceptable salt, X is hydrogen, dialkylaminomethyl, lower alkyl, lower alkoxy, aryl, substituted aryl, halogen, cyano, nitro, trihaloalkyl, --NR.sub.1 R.sub.2 or --NHCOR.sub.1 where R.sub.1 and R.sub.2 are hydrogen, lower alkyl or NH.sub.2 and n is 0-5.