| abstract |
The various tautomeric forms of (I):- (where R is alkyl, cycloalkyl, aralkyl or aryl, all opt. substd. but excluding unsubstd. phenyl; R1 and R2 are H or opt. substs. alkyl or aryl and R4 is H or the acid radical of an organic carboxyacid, are preped. by methods usual for such structures. Partic., R is 1-4C alkyl, 5-6C cycloalkyl, diphenylalyl, nitrophenyl-, methylphenyl- benzyl- or dimethoxyphenethyl, R1 and R2 are H and R4 acetyl. propionyl, hydroxybenzolyl or beta-piperidino-propionyl.n[FR2068471A1] |