Synthetic approaches towards novel 3-pyrazolidinone derivatives functionalized at positions N(1) and/or C(5) were studied. 5-Aminoalkyl-3-pyrazolidinones were prepared in four steps from N-protected glycines via Masamune-Claisen homologation, reduction, O-mesylation, and cyclisation with a hydrazinederivative. The free amines were prepared by acidolytic deprotection. Title compound was also prepared
lic acid, (±)-3, via nucleophilic addition of phenylhydrazine to dimethyl maleate, followed by cyclization of the resulting hydrazine-diester. The resolution of (±)-3 was achieved via diastereomeric salts employing (R)- and (S)-α-methylbenzylamine as resolving agent. Preferential crystallization of the like (R,R)- and (S,S)- salts allowed the isolation of the desired enantiomerically pure (R)- and
Compounds having the formula ##STR1## and basic salts thereof, wherein R.sub.1 is hydrogen, alkyl, aryl, arylalkyl or ##STR2## wherein R.sub.5 is alkyl or aryl; R.sub.2 is hydrogen or alkyl; R.sub.3 is hydrogen, alkyl, aryl or arylalkyl; and R.sub.4 is hydrogen, alkyl, or arylalkyl; have useful hypotensive activity.
Opticalresolution of racemic 5-oxo-1-phenyl-pyrazolidine-3-carboxylic acid 2 with L-amino acid methyl ester via the diastereomers formation was investigated. Treatment of racemic 5-oxo-1-phenylpyrazolidine-3-carboxylic acid 2 with L-valine methyl ester gave diastereomers with a total yield of 86%. The diastereomeric dipeptides can be easily separated by flash column chromatography. Acidic cleavage