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D Velmurugan

Publications and source records attributed to D Velmurugan.

At least 37 records · Page 2Linked to original sources
PubMed2002

5-[Acetamido(phenyl)methyl]-5-methylimidazolidine-2,4-dione.

The title compound, alternatively named N-[(4-methyl-2,5-dioxoimidazolidin-4-yl)(phenyl)methyl]acetamide, C(13)H(15)N(3)O(3), crystallizes in the centrosymmetric space group P2(1)/c with one molocule in the asymmetric unit. The imidazolidine-2,4-dione system is essentially planar, as evidenced by NMR studies. The dihedral angle between the planes of the imidazolidine and phenyl rings is 23.3 (1) degrees, while the dihedral angle between the acetamide side chain and the imidazolidine ring is 60.7 (1) degrees. The molecular structure and packing is stabilized by C-H.O and N-H.O interactions. Intermolecular hydrogen bonds form cyclic dimers, with graph-set descriptor R(2)(2)(8), and a chain of C(7).

Journal Article↗
PubMed2002

Trimethyl[3-methyl-1-(o-tolenesulfonyl)indol-2-ylmethyl]ammonium iodide and benzyl[3-bromo-1-(phenylsulfonyl)indol-2-ylmethyl]tolylamine.

The title compounds, C(20)H(25)N(2)O(2)S(+).I(-), (I), and C(29)H(25)BrN(2)O(2)S, (II), respectively, both crystallize in space group P-1. The pyrrole ring subtends an angle with the sulfonyl group of 33.6 degrees in (I) and 21.5 degrees in (II). The phenyl ring of the sulfonyl substituent makes a dihedral angle with the best plane of the indole moiety of 81.6 degrees in (I) and 67.2 degrees in (II). The lengthening or shortening of the C-N bond distances in both compounds is due to the electron-withdrawing character of the phenylsulfonyl group. The S atoms are in distorted tetrahedral configurations. The molecular structures are stabilized by C-H.O and C-H.I interactions in (I), and by C-H.O and C-H.N interactions in (II).

Journal Article↗
PubMed2002

Diethyl [3-[beta-(2,4-dichlorophenyl)vinyl]-N-(phenylsulfonyl)indol-2-ylmethyl]phosphonate and diethyl [3-[beta-(4-bromophenyl)vinyl]-N-(phenylsulfonyl)indol-2-ylmethyl]phosphonate.

The title compounds, C(27)H(26)Cl(2)NO(5)PS, (I), and C(27)H(27)BrNO(5)PS, (II), respectively, crystallize in the centrosymmetric space group P2(1)/n with one molecule in the asymmetric unit in each case. The dihedral angle between the benzene and pyrrole rings is 2.1 (1) degrees in (I) and 0.9 (2) degrees in (II). The phenylsulfonyl group is orthogonal to the halophenyl moiety, with a dihedral angle of 82.0 (1) degrees in (I) and 78.7 (2) degrees in (II). In both compounds, the molecular structures and packing are stabilized by C-H...O and C-H...halogen interactions. The intermolecular hydrogen bonds in (I) form cyclic dimers with graph-set descriptors R(2)(1)(10) and R(2)(2)(8) about a 2(1) axis, and those in (II) form a C(2)(2)(20) chain.

Crystallography, X-Ray↗
PubMed2002

Ethyl beta-[2-[4-(dimethylamino)phenyliminomethyl]-1-(phenylsulfonyl)indol-3-yl]acrylate.

The title compound, C(28)H(27)N(3)O(4)S, crystallizes in the centrosymmetric space group P2(1)/n, with one molecule in the asymmetric unit. In the indole ring, the dihedral angle between the fused rings is 3.6 (1) degrees. The phenyl ring of the sulfonyl substituent makes a dihedral angle of 79.2 (1) degrees with the best plane of the indole moiety. The phenyl ring of the dimethylaminophenyl group is orthogonal to the phenyl ring of the phenylsulfonyl group. The dihedral angle formed by the weighted least-squares planes through the pyrrole ring and the phenyl ring of the dimethylaminophenyl group is 7.8 (1) degrees. The molecular structure is stabilized by C-H.O and C-H.N interactions.

Acrylates↗
PubMed2002

2-[1-(Phenylsulfonyl)ethyl]benzoic acid and 2-[1-(phenylsulfonyl)propyl]benzoic acid.

In the title acids, C(15)H(14)O(4)S, (I), and C(16)H(16)O(4)S, (II), respectively, the angle between the planes of the benzene ring and the carboxyl group is 13.7 (1) degrees for (I) and 21.3 (1) degrees for (II). The molecular structures are stabilized by intramolecular C-H.O hydrogen bonds. The crystal packing is stabilized by a single O-H.O hydrogen bond in both compounds, in which the O and H atoms are ordered; H.O 1.87 A for (I) and 1.83 A for (II), O.O 2.680 (2) A for (I) and 2.652 (3) A for (II), and O-H.O 172 degrees for (I) and 175 degrees for (II). The hydrogen bond forms a cyclic dimer, with graph-set descriptor R(2)(2)(8), about a centre of symmetry.

Benzoates↗
PubMed2002

Photochemistry of arylidene-beta-ionones: a highly efficient route to novel tricyclic ketones through intramolecular, exoselective photochemical (4 + 2) cycloadditions, occurring only in an aqueous-organic solvent.

(E,E)-Arylidene-beta-ionones (1a-f) are converted to 1,7,7-trimethyl-3-(E-2'-arylethenyl)-2-oxabicyclo[4.4.0]deca-3,5-dienes (3a-f, approximately 90%) by irradiating in anhydrous solvents. Irradiation of (3a-f) in aqueous methanol results in Z,E-arylidene-beta-ionones (2), through retro-electrocyclization, which undergoes an intramolecular, exo-selective [4 + 2] photocycloaddition leading to 11-(exo)-aryl-1,7,7-trimethyl-tricyclo[4.4.0.1(2,4)]undec-5-ene-3-ones (8a-f, 60-80%). The latter rearrange over silica gel to afford, quantitatively, 5-aryl-7,11,11-trimethyl-tricyclo[5.4.0.0(3,6)]undec-1-ene-4-ones (5a-f). Irradiation of 1a-f in aqueous methanol leads to 8a-f, except in case of 1c,f wherein formation, respectively, of tricyclic ketones 9c (55%) and 9f (80%), derived from photodeconjugation in 2, followed by intramolecular [4 + 2] cycloaddition, is observed.

Journal Article↗
PubMed2002

Three tetrahydroisoquinolinedione derivatives.

N-(2-Chlorobenzyl)-1,2,3,4-tetrahydroisoquinoline-1,3-dione, C(16)H(12)ClNO(2), crystallizes in P2(1)/n with three crystallographically independent molecules in the asymmetric unit, which differ slightly in conformation, N-(2-bromo-4-methylphenyl)-1,2,3,4-tetrahydroisoquinoline-1,3-dione, C(16)H(12)BrNO(2), crystallizes in P2(1)/n with one molecule in the asymmetric unit and N-(2,3-dichlorophenyl)-1,2,3,4-tetrahydroisoquinoline-1,3-dione, C(15)H(9)Cl(2)NO(2), crystallizes in P2(1)/c with one molecule in the asymmetric unit. In all three structures, the heterocyclic rings adopt approximately planar conformations. The pyridine rings are orthogonal to the substituted phenyl rings. In all three structures, the crystal packing is stabilized by intermolecular C-H...O hydrogen bonds.

Hydrogen Bonding↗
PubMed2002

Peptide design using omega-amino acids: unusual turn structures nucleated by an N-terminal single gamma-aminobutyric acid residue in short model peptides.

Incorporation of omega-amino acids into peptide sequences plays an important role in designing peptides with modified backbone conformation and enhanced stability against proteolysis. The present study establishes the presence of unusual turns involving 12-membered hydrogen bonded rings in terminally blocked tri- and tetrapeptides. X-ray diffraction analysis of single crystals and NMR studies have been used to probe the three-dimensional structures of two terminally protected short peptides, Boc-gamma-Abu(1)-Aib(2)-Ala(3)-OMe 1 and Boc-gamma-Abu(1)-Aib(2)-Ala(3)-Aib(4)-OMe 2 (gamma-Abu = gamma-aminobutyric acid), in which conformationally flexible omega-amino acids (gamma-Abu) and conformationally restricted alpha-aminoisobutyric acid (Aib) residues are positioned contiguously. The crystal structures of both peptides 1 and 2 exhibit unusual turns composed of 12-membered hydrogen bonded rings involving C [double bond] O from the Boc-group and Ala(3) NH. A type I' beta-turn was observed in the structure of peptide 2 adjacent to the unusual turn with a hydrogen bond between gamma-Abu(1) C [double bond] O and Aib(4) NH. The crystals of peptide 1 are in the space group P2(1), a = 9.3020(10) A, b = 23.785(2) A, c = 10.022(3) A, beta = 101.35 degrees(4), Z = 4, R = 5.7%, and R(w) = 14.5%. Similarly, the crystals of peptide 2 are in the space group C2, a = 19.0772(6) A, b = 8.7883(2) A, c = 16.7758(3) A, beta = 110.7910 degrees(10), Z = 4, R = 6.71%, and R(w) = 15.11%. The unusual turn in both peptides 1 and 2 are retained in solution as is evident from NMR studies in CDCl(3). The role of the adjacently located Aib residue to nucleate the 12-membered hydrogen bonded ring is also addressed.

Amino Acids↗
PubMed2001

3-(p-chlorophenyl)-4-phenyl-4,5-dihydroisoxazole-5-spiro-2'-1',2',3',4'-tetrahydronaphthalen-1'-one.

In the title compound, C24H18ClNO2, the phenyl ring and the tetralone moiety are approximately orthogonal to the isoxazoline ring. The isoxazoline ring adopts an envelope conformation, while the cyclohexenone ring of the tetralone moiety has an intermediate sofa/half-chair conformation. In this structure, one C--H...N intermolecular and two C--H...O intramolecular hydrogen bonds occur; the H.A distances are 2.60, and 2.35 and 2.57 A, respectively. The molecules are held together by an intermolecular C--H...N hydrogen bond, forming a one-dimensional chain along the [100] direction.

Antineoplastic Agents↗
PubMed2001

10-(4-fluorophenyl)-3,3,6,6,9-pentamethyl-3,4,6,7,9,10-hexahydroacridine-1,8(2h,5h)-dione and 10-(4-fluorophenyl)-3,3,6,6-tetramethyl-9-propyl-3,4,6,7,9,10-hexahydroacridine-1,8(2h,5h)-dione.

10-(4-fluorophenyl)-3,3,6,6,9-pentamethyl-3,4,6,7,9,10-hexahydroacridine-1,8(2H,5H)-dione, C24H28FNO2, (I), crystallizes with two crystallographically independent molecules (which differ slightly in conformation), while 10-(4-fluorophenyl)-9-propyl-3,3,6,6-tetramethyl-3,4,6,7,9,10-hexahydroacridine-1,8(2H,5H)-dione, C26H32FNO2, (II), crystallizes with one molecule per asymmetric unit. In both structures, the central ring in the acridine moiety is in a sofa conformation, while the outer rings adopt intermediate half-chair/sofa conformations. The central pyridine ring is orthogonal to the substituted phenyl ring. In both structures, the packing of the crystal is stabilized by C--H...O intermolecular hydrogen bonds.

Acridines↗
PubMed2001

3-amino-4'-methyl-5-ethylbiphenyl-2,4-dicarbonitrile and 3-amino-4'-(n,n-diethylamino)-5-ethylbiphenyl-2,4-dicarbonitrile.

In the title compounds, C17H15N3 and C20H22N4, the methyl derivative crystallizes with two molecules in the asymmetric unit, while the N,N-diethylamino derivative crystallizes with one molecule per asymmetric unit. The biphenyl twist angle for both molecular structures is approximately 45 degrees. The molecular packing is stabilized by N-H...N hydrogen bonds.

Journal Article↗
PubMed2001

5-amino-4-(4-diethylaminophenyl)-2-(4-hydroxyphenyl)-7-(pyrrolidin-1-yl)-1,6-naphthyridine-8-carbonitrile.

In the title compound, C29H30N6O, the naphthyridine moiety is planar with a dihedral angle between the fused rings of 1.9 (1) degrees. The phenol ring is nearly coplanar, while the diethylaminophenyl substituent is orthogonal to the central naphthyridine ring and the pyrrolidine ring makes an angle of 11.2 (1) degrees with it. The O atom of the hydroxy substituent is coplanar with the phenyl ring to which it is attached. The molecular structure is stabilized by a C-H...N-type intramolecular hydrogen bond and the packing is stabilized by intermolecular C-H...pi, O-H...N and N-H...O hydrogen bonds.

Crystallography, X-Ray↗
PubMed2001

N-Methyl-N-(1-phenylsulfonylindol-2-ylmethyl)aniline.

In the title compound, 2-[(methylphenylamino)methyl]-1-(phenylsulfonyl)indole, C22H20N2O2S, the indole system is not strictly planar and the dihedral angle between the fused rings is 2.7 (1) degrees. The angles around the S atom of the sulfonyl substituent deviate significantly from the ideal value for tetrahedral geometry. The pyramidalization at the indole N atom is very small. Of the two C-H...O interactions, one influences the orientation of indole with respect to the sulfonyl group and the other determines the orientation of the phenyl bound to sulfonyl. The phenyl ring of the sulfonyl substituent makes a dihedral angle of 89.6 (1) degrees with the best plane of the indole. The molecular packing is stabilized by C-H...pi and C-H...O hydrogen bonds.

Aniline Compounds↗
PubMed2000

Conformational choice at alpha,alpha-di-n-propylglycine residues: helical or fully extended structures?

The conformational analysis of peptides containing a single alpha, alpha-di-n-propylglycine (Dpg) residue incorporated into valine-rich sequences has been undertaken in order to delineate the possible role of sequence effects in stabilizing fully extended (C(5)) or local helical conformations at this residue. The three peptides Boc-Val-Dpg-Val-OMe (3), Boc-Val-Val-Dpg-Val-OMe (4), Boc-Val-Val-Dpg-Val-Val-OMe (5), have been studied by (1)H-nmr methods in chloroform (CDCl(3)) and dimethylsulfoxide (DMSO) solutions. Even in a relatively poorly solvating medium like CDCl(3), all the valine NH groups appear to be solvent-exposed, suggesting an absence of folded beta-turn conformations. However, in both CDCl(3) and DMSO the Dpg NH groups in all the three peptides appear to behave like apparently solvent-inaccessible groups. In fully extended C(5) conformations, the proximity of the NH and CO groups of Dpg may preclude effective solvation due to a combination of stereoelectronic factors. Nuclear Overhauser effects provide support for the largely extended backbones. The crystal structure of peptide 3 reveals an extended conformation at Dpg (2) with straight phi = -176 degrees, psi = 180 degrees. A correlation between the crystallographically observed backbone conformation and solution nmr parameters in DMSO has been attempted using available data. Dpg residues placed in poor helix stabilizing environments may be expected to favor a local C(5) conformation.

Amino Acid Sequence↗
PubMed2000

Context-dependent conformation of diethylglycine residues in peptides.

Diethylglycine (Deg) residues incorporated into peptides can stabilize fully extended (C5) or helical conformations. The conformations of three tetrapeptides Boc-Xxx-Deg-Xxx-Deg-OMe (Xxx=Gly, GD4; Leu, LD4 and Pro, PD4) have been investigated by NMR. In the Gly and Leu peptides, NOE data suggest that the local conformations at the Deg residues are fully extended. Low temperature coefficients for the Deg(2) and Deg(4) NH groups are consistent with their inaccessibility to solvent, in a C5 conformation. NMR evidence supports a folded beta-turn conformation involving Deg(2)-Gly(3), stabilized by a 4-->1 intramolecular hydrogen bond between Pro(1) CO and Deg(4) NH in the proline containing peptide (PD4). The crystal structure of GD4 reveals a hydrated multiple turn conformation with Gly(1)-Deg(2) adopting a distorted type II/II' conformation, while the Deg(2)-Pro(3) segment adopts a type III/III' structure. A lone water molecule is inserted into the potential 4-->1 hydrogen bond of the Gly(1)-Deg(2) beta-turn.

Amino Acid Motifs↗
PubMed2000

Two benzoylaminoacridinedione derivatives

The title compounds, 10-benzoylamino-1,2,3,4,5,6,7,8,9, 10-decahydroacridine-1,8-dione monohydrate, C(20)H(20)N(2)O(3).H(2)O, and 10-p-toluoylamino-1,2,3,4,5,6,7,8,9,10-decahydroacridine-1, 8-dione monohydrate, C(21)H(22)N(2)O(3).H(2)O, consist of partially hydrogenated acridine moieties with one benzoylamino substituent on the central ring. The acridine moiety suffers considerable deviations from planarity. The central ring in the acridine moiety is a boat, while the outer rings adopt sofa conformations.

Journal Article↗