Tosyl-L-proline

2,4-Dinitro-N-(2-phenylethyl)aniline, C14H13N3O4, (I), crystallizes with one independent molecule in the asymmetric unit. The adjacent amine and nitro groups form an intramolecular N-H...O hydrogen bond. The anti conformation about the ethyl C-C bond leads to the phenyl and aniline rings being essentially parallel. Molecules are linked into dimers by intermolecular N-H...O hydrogen bonds, such that each amine H atom participates in a three-centre interaction with two nitro O atoms. Though the dimers pack so that the arene rings of adjacent molecules are parallel, the rings are staggered and π-π interactions do not appear to be favoured. 4,6-Dinitro-N,N'-bis(2-phenylethyl)benzene-1,3-diamine, C22H22N4O4, (II), differs from (I) in the presence of a second 2-phenylethylamine group on the substituted ring. Compound (II) also crystallizes with one unique molecule in the asymmetric unit. Both amine groups are involved in intramolecular N-H...O hydrogen bonds with adjacent nitro groups. Although one ethyl group adopts an anti conformation as in (I), the other is gauche, with the result that the pendant phenyl rings are not parallel. The amine group that is part of the gauche conformation participates in a three-centre N-H...O hydrogen bond with the nitro group of a neighbouring molecule, leading to dimers as in (I). The other amine H atom does not form any intermolecular hydrogen bonds. The packing leads to separations of ca 3.4 Å of the parallel anti phenyl and aminobenzene rings. 2-Cyano-4-nitro-N-(2-phenylethyl)aniline, C15H13N3O2, (III), differs from (I) only in having a cyano group in place of the 2-nitro group. The absence of the adjacent nitro group eliminates the intramolecular N-H...O hydrogen bond. Molecules of (III) adopt the same anti conformation about the ethyl group as in (I), but crystallize in the higher-symmetry monoclinic space group P21/n. The molecules are linked into dimers via N-H...N amine-cyano hydrogen bonds, while the nitro groups are not involved in any N-H...O interactions. Owing to the different symmetry, the molecules pack in a herringbone pattern with fewer face-to-face interactions between the rings. The closest such interactions are about 3.5 Å between rings that are largely slipped past one another. 4-Methylsulfonyl-2-nitro-N-(2-phenylethyl)aniline, C15H16N2O4S, (IV), differs from (I) in having a methylsulfonyl group in place of the 4-nitro group. The intramolecular N-H...O hydrogen bond is present as in (I). However, unlike (I), the conformation about the ethyl group is gauche, so the two arene rings are nearly perpendicular rather than parallel. The packing is significantly different from the other three structures in that there are no intermolecular hydrogen bonds involving the N-H groups. The molecules are arranged in tetragonal columns running along the c axis, with the aniline rings mostly parallel and separated by ca 3.7 Å. Taken together, these structures demonstrate that modest changes in functional groups cause significant differences in molecular conformation, intermolecular interactions and packing.

The structures of the open-chain amide carboxylic acid rac-cis-2-[(2-methoxyphenyl)carbamoyl]cyclohexane-1-carboxylic acid, C(15)H(19)NO(4), (I), and the cyclic imides rac-cis-2-(4-methoxyphenyl)-3a,4,5,6,7,7a-hexahydroisoindole-1,3-dione, C(15)H(17)NO(3), (II), chiral cis-3-(1,3-dioxo-3a,4,5,6,7,7a-hexahydroisoindol-2-yl)benzoic acid, C(15)H(15)NO(4), (III), and rac-cis-4-(1,3-dioxo-3a,4,5,6,7,7a-hexahydroisoindol-2-yl)benzoic acid monohydrate, C(15)H(15)NO(4)·H(2)O, (IV), are reported. In the amide acid (I), the phenylcarbamoyl group is essentially planar [maximum deviation from the least-squares plane = 0.060 (1) Å for the amide O atom] and the molecules form discrete centrosymmetric dimers through intermolecular cyclic carboxy-carboxy O-H···O hydrogen-bonding interactions [graph-set notation R(2)(2)(8)]. The cyclic imides (II)-(IV) are conformationally similar, with comparable benzene ring rotations about the imide N-C(ar) bond [dihedral angles between the benzene and isoindole rings = 51.55 (7)° in (II), 59.22 (12)° in (III) and 51.99 (14)° in (IV)]. Unlike (II), in which only weak intermolecular C-H···O(imide) hydrogen bonding is present, the crystal packing of imides (III) and (IV) shows strong intermolecular carboxylic acid O-H···O hydrogen-bonding associations. With (III), these involve imide O-atom acceptors, giving one-dimensional zigzag chains [graph-set C(9)], while with the monohydrate (IV), the hydrogen bond involves the partially disordered water molecule which also bridges molecules through both imide and carboxy O-atom acceptors in a cyclic R(4)(4)(12) association, giving a two-dimensional sheet structure. The structures reported here expand the structural database for compounds of this series formed from the facile reaction of cis-cyclohexane-1,2-dicarboxylic anhydride with substituted anilines, in which there is a much larger incidence of cyclic imides compared to amide carboxylic acids.

The crystal structures of captopril {systematic name: (2S)-1-[(2S)-2-methyl-3-sulfanylpropanoyl]pyrrolidine-2-carboxylic acid}, C(9)H(15)NO(3)S, (1), and its dimer disulfide metabolite, 1,1'-{disulfanediylbis[(2S)-2-methyl-1-oxopropane-3,1-diyl]}bis-L-proline, C(18)H(28)N(2)O(6)S(2), (2), were determined by single-crystal X-ray diffraction analysis. Compound (1) crystallizes in the orthorhombic space group P2(1)2(1)2(1), while compound (2) crystallizes in the monoclinic space group P2(1), both with one molecule per asymmetric unit. The molecular geometries of (1) and (2) are quite similar, but certain differences appear in the conformations of the five-membered proline rings and the side chains containing the sulfhydryl group. The proline ring adopts an envelope conformation in (1), while in (2) it exists in envelope and slightly deformed half-chair conformations. The conformation adopted by the side chain is extended in (1) and folded in (2). A minimum-energy conformational search using Monte Carlo methods in the aqueous phase reveals that the optimized conformations of the title compounds differ from those determined crystallographically, which depend on their immediate environment. Intermolecular O-H...O and relatively weak C-H...O interactions seem to be effective in both structures and, together with S-H...O and C-H...S contacts, they create three-dimensional networks.