P. Roychowdhury

Synthesis and spectroscopic characterisation of cobalt(III) complexes with S-benzyl dithiocarbazate of 5-methyl-3-formyl pyrazole (HMPzSB): X-ray crystal structure of [Co(MPzSB)2]Cl

Abstract The coordination mode of the title ligand, HMPzSB (synthesized for the first time and characterised by elemental analysis, mass, IR and PMR spectral parameters), is reported by solid state isolation and physicochemical identification of cobalt(III) complexes, [Co(MPzSB)2]X (X = Cl, ClO4 and BF4). Electronic spectral features of these diamagnetic CoIII species classify them as six-coordinate distorted octahedral ones. IR spectra (4000-200 cm−1) of HMPzSB and its complexes are indicative of an uninegative tridentate NNS function of the title ligand through the Pyrazolyl (2N) nitrogen, azomethine nitrogen and thiolato sulphur atom. 1H-NMR data (in d6-DMSO at 300 MHz) of the uncomplexed ligand and its CoIII species are commensurate with the tridenticity (NNS) of the deprotonated form of HMPzSB. X-ray crystallographic studies of [Co(MPzSB)2]Cl has authenticated that the geometry of the species is distorted octahedral, as envisaged, with the two deprotonated primary ligand systems (MPzSB−). The CoN (azomethine) and CoN (pyrazolyl) bond lengths are 1.898(4) & 1.954(5) A and 1.903(4) & 1.916(5) A in ligand A & B, respectively where as that of CoS (thiolato) is 2.217(2) and 2.255(2) A in the two ligands. The extended planarity of the dithiocarbazate moiety and the pyrazolyl ring of the primary ligand system are maintained because of the ligation phenomenon to CoIII.

Synthesis and crystal structures of 5-amino-1-(2-hydroxyethyl)imidazole-4-carboxamide and 5-amino-1-(2-chloroethyl)-4-cyanoimidazole

Both 5-amino-1-(2-hydroxyethyl)imidazole-4-carboxamide (AHIC) and 5-amino-1-(2-chloroethyl)-4-cyanoimidazole (ACCI) have been synthesized and crystallized in the monoclinic space group P21/c, Z = 4, with a = 8.420(2), b = 9.759(2), c = 10.583(2) Å, β = 111.80(2)° for AHIC and a = 6.139(1), b = 8.522(2), c = 15.156(3) Å, β = 96.71(2)° for ACCI. Differences in the molecular geometries of the two compounds are attributed to the differences in the substituents at the 1- and 4-positions of the imidazole ring. The molecular conformation of AHIC is stabilized by intramolecular hydrogen bonding between the 5-amino and the vicinal carboxamide moiety, resulting in an extended planar structural pattern. The presence of the cyano group in the 4-position of ACCI prevents the formation of such an intramolecular hydrogen bond. Both the crystal structures are stabilized by networks of intermolecular hydrogen bonds.

Homology modelling of the ligand binding domain of mineralocorticoid receptor: close structural kinship with glucocorticoid receptor ligand binding domain and their similar binding mode with DOC (de-oxy corticosterone).

Abstract Mineralocorticoids play a major role in regulating sodium and potassium homeostasis and also contribute to the control of blood pressure and in some physiological disorders. The physiological effects of this class of corticosteroids are mediated by ligand-induced nuclear transcription factor, the mineralocorticoid receptor(MR)/glucocorticoid receptor(GR), a member of the steroid/nuclear receptor superfamily. Although the MR interacts with both glucocorticoids and mineralocorticoids, the GR interacts specifically with glucocorticoids. The three dimensional structure of progesterone complexed to its receptor revealed in X-ray diffraction method is utilised to develop a homology model of human mineralocorticoid receptor ligand binding domain (hMR LBD) in a similar fashion as mouse GR LBD was developed previously. The secondary structure of hMR LBD contains eleven helices, eight turns and four sheets. This receptor contains a long helix, H9, with thirty four residues. The 12-residue C-terminal extension (residues 973–984) of hMR LBD, which is essential for hormone binding, is tightly fixed in position by an antiparallel β-sheet interaction. The three dimensional model reveals two polar sites located at the extremities of the elongated hydrophobic ligand-binding pocket (LBP). De-oxy corticosterone (DOC) is docked to the LBPs of both hMR LBD and mGR LBD. The difference accessible surface area (DASA) study revealed the interaction zones of both the receptors in complex with DOC. Observations relating to the native and complex proteins revealed a close structural kinship between hMR LBD and mGR LBD.

X-Ray crystal structure of bis-(p-nitroacetophenone-4,6-dimethyl-2-pyrimidyl hydrazone) copper(i) perchlorate

Abstract The title copper(I) complex of a substituted pyrimidyl hydrazone has been synthesized and characterized by X-ray diffraction. The structure has been shown to contain one central Cu atom bonded to four N atoms in a tetrahedral geometry with two hydrazinic N atoms and two pyrimidyl ring N atoms. The structure also proves that the pyrimidine ring and the phenyl ring of the acetophenone moiety are linked by an azomethine linkage. Copyright

Structure of de-oxy corticosterone (4-pregnen-21-ol-3, 20-dione)

Synthetic steroid de-oxy corticosterone (4-pregnen-21-ol-3,20-dione) crystallizes in the monoclinic space group P21, with a = 11.706(2); b = 11.171(3), c = 13.966(3) Å, and β = 100.94(2)°, Z = 4. Ring A tends to acquire the conformation of a half-boat, rings B and C are in the chair configuration, and ring D is a 13β, 14α-half-chair. The ring junctions B/C and C/D are both trans, whereas the ring junction A/B is quasi-trans. The molecule as a whole is slightly convex toward the β-side, with an angle of 16.01(0.36)° between the C10--C19 and C13--C18 vectors. Molecular packing and stacking interactions play the major role in structural association. Cohesion of the crystal is due to van der Waals interactions.

5-Amino-1-[2-(diethylamino)ethyl]-1H-imidazole-4-carboxamide

Intramolecular hydrogen bonds influence the molecular conformation of the title compound, C 10 H 19 N 5 O, resulting in an extended planar hydrogen-bonded heterocyclic ring structure. The bulky diethylaminoethyl group adopts a butterfly conformation. The stabilization of the crystal structure is supported by an extensive network of intermolecular hydrogen bonds.

5-Amino-1-benzyl-4-cyano-3-methylimidazolium toluene-p-sulfonate

The title compound, C12H13N4+·C7H7O3S−, contains an imidazolium cation and a toluene-p-sulfonate anion in the asymmetric unit. Hydrogen-bonded dimers are formed between the cyano and amino groups of inversion-related imidazolium cations.

Structure of de-oxy corticosterone-21-hemisuccinate

Synthetic glucocorticoid de-oxy corticosterone-21-hemisuccinate crystallizes in the monoclinic space group C2, with a = 21.896(2), b = 7.596(3) and c = 14.291(3) Å, Z = 4. Ring A is a distorted half chair, ring B and C are in the chair configuration and ring D is in the 14α-half chair configuration. The ring junctions B/C and C/D are both trans. The molecule as a whole is slightly convex towards the β-side, with an angle of 18.4(2)° between the C(10)--C(19) and C(13)--C(18) vectors. In addition to packing and stacking interaction, intermolecular hydrogen bonding plays an important role in structural association. The X-ray structure determination of the title compound was undertaken to study its high binding affinity to serum protein like globulin.

N-Benzenesulfonylglycylglycine, (I), and Tetrakis(μ-N-benzenesulfonylglycylglycinato)bis[aquacopper(II)](Cu—Cu)–Water (1/4), (II)

Each Cu II ion in [{Cu(H 2 O)} 2 (μ-C 10 H 11 N 2 O 5 S) 4 ].4H 2 O, (II), is coordinated to its centrosymmetric counterpart, the equatorial carbonyl and carboxylic O atoms of two N-benzenesulfonylglycylglycinate moieties and their centrosymmetric counterparts and to an axial water O atom. The centrosymmetrically related Cu II ions are linked by bridges of 2.641(1)A to form dimeric dinuclear units. In both (I) (C 10 H 12 N 2 O 5 S) and (II), the terminal and peptide N atoms are in cis conformation. The carboxylic group is localized in (I) but a complete delocalization of this group has been observed in the metal complex. When coordinated by the metal ion, the N-benzenesulfonylglycylglycine moieties undergo major conformational changes about the N-C α bonds along the peptide backbone.

Synthesis and crystal structure of (5-amino-4-carboxamidoimidazol-1-yl) acetamide, a possible PDE inhibitor

The crystal structure of 2-(5-amino-4-carboxamidoimidazol-1-yl)acetamide has been determined from X-ray diffractometric data, and refined to anR-value of 0.057 with 1179 observed reflections. Intramolecular hydrogen bonding between the 5-amino group and the vicinal carboxamide moiety stabilizes the molecular conformation and forms an extended planar structural pattern.