The diastereoisomers methyl 5-(S)-[2-(R)/(S)-methoxycarbonyl)-2,3,4,5-tetrahydropyrrol-1-ylcarbonyl]-1-(4-methylphenyl)-4,5-dihydropyrazole-3-carboxylate

The title diastereoisomers, methyl 5-(S)-[2-(S)-methoxycarbonyl)-2,3,4,5-tetrahydropyrrol-1-ylcarbonyl]-1-(4-methyl- phenyl)-4,5-dihydropyrazole-3-carboxylate and methyl 5-(S)[2-(R)-methoxycarbonyl)-2,3,4,5-tetrahydropyrrol-1-ylcar- bonyl]-1-(4-methylphenyl)-4,5-dihydropyrazole-3-carboxyl- ate, both C19H23N3O5, have been studied in two crystalline forms. The first form, methyl 5-(S)-[2-(S)-methoxycarbonyl)2,3,4,5-tetrahydropyrrol-1-ylcarbonyl]-1-(4-methylphenyl)- 4,5-dihydropyrazole-3-carboxylate-methyl 5-(S)-[2-(R)-methoxycarbonyl)-2,3,4,5-tetrahydropyrrol-1-ylcarbonyl]-1-(4-methylphenyl)-4,5-dihydropyrazole-3-carboxylate (1/1), 2(S),5(S)-C19H23N3O5.2(R),5(S)-C19H23N3O5, contains both S,S and S,R isomers, while the second, methyl 5-(S)-[2-(S)methoxycarbonyl)-2,3,4,5-tetrahydropyrrol-1-ylcarbonyl]- 1-(4-methylphenyl)-4,5-dihydropyrazole-3-carboxylate, 2(S),5(S)-C19H23N3O5, is the pure S,S isomer. The S,S isomers in the two structures show very similar geometries, the maximum difference being about 15degrees on one torsion angle. The differences between the S,S and S,R isomers, apart from those due to the inversion of one chiral centre, are more remarkable, and are partially due to a possible rotational disorder of the 2-(methoxycarbonyl)tetrahydropyrrole group.