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Biomedical subjects

Daniel E Lynch

Publications and source records attributed to Daniel E Lynch.

12 recordsLinked to original sources
PubMed2006

Hydrogen-bonding patterns in trimethoprim picolinate and 2-amino-4,6-dimethylpyrimidinium picolinate hemihydrate.

In the title compounds, namely 2,4-diamino-5-[(3,4,5-trimethoxyphenyl)methyl]pyrimidin-1-ium pyridine-2-carboxylate, C14H19N4O3+.C6H4NO2-, (I), and 2-amino-4,6-dimethylpyrimidin-1-ium pyridine-2-carboxylate hemihydrate, C6H10N3+.C6H4NO2-.0.5H2O, (II), the trimethoprim and 2-amino-4,6-dimethylpyrimidin-1-ium cations are protonated at one of the pyrimidine N atoms. In (I), bifurcated hydrogen bonds are observed between a picolinate O atom, the protonated N atom and the 2-amino group; the graph-set designator is R2(1)(6). The pyrimidine moieties of the trimethoprim cations are centrosymmetrically paired through a pair of N-H...N hydrogen bonds. In addition to the base pairing, one of the picolinate O atoms bridges the 2- and 4-amino groups on either side of the paired bases, resulting in a complementary DADA array. In (II), the carboxylate group of the picolinate anion binds with the protonated pyrimidine N atom and the 2-amino group of the pyrimidine moiety through a pair of N-H...O hydrogen bonds, leading to the common ring motif R2(2)(8). The water molecule, which resides on a twofold rotation axis, bridges the carboxylate group of the picolinate anion via O-H...O hydrogen bonds.

Crystallography↗
PubMed2005

Preparation of sub-micrometer silica shells using poly(1-methylpyrrol-2-ylsquaraine).

Poly(1-methylpyrrol-2-ylsquaraine) precipitates from reaction solution as uniformly spherical particles with a diameter of 1.3 microm. Upon heating, the particles reduce in diameter until extinction at approximately 630 degrees C. Treatment of the particles with 9:1 tetraethoxysilane:ethanol solution, and subsequent hydrolysis in dilute acid, results in a polymer core-silica shell structure. Removal of the core, upon heating to 660 degrees C, results in an amorphous silica shell with a diameter half that of the initial template sphere. It has been found that the silica shells produced by this method are able to encapsulate organic dyes upon soaking of the shells in chloroform solutions of the dyes, and further washings with fresh chloroform did not remove the dyes. The production of crystalline titanium dioxide shells was also achieved through the use of the polysquaraine particles as a spherical template.

Journal Article↗
PubMed2004

Geometry of the 2-aminoheterocyclic-carboxylic acid R2(2)(8) graph set: implications for crystal engineering.

The geometry of the R2(2)(8) graph set formed between a 2-aminoheterocyclic ring containing an Nsp2 atom (in the 1-position of the ring) and a carboxylic acid has been studied. Collating data from known co-crystal structures containing five- and six-membered heterocyclic rings from the Cambridge Structural Database revealed unexpected differences between two kinds of non-hydrogen contact distances, and between specific bond distances and angles of the heterocycle. Not only were the interatomic non-hydrogen distances between the N atoms (heterocycle) and O atoms (carboxylate) asymmetric, but also the 2-amino N atom (N21) to the heterocyclic C atom (C2) bond was shorter than the C2 to N1sp2 bond. However, this shortening of the C2-N21 bond was not observed in the examples where N21 was substituted with a non-H atom. For the six-membered rings the data also showed that as the C2-N21 bond shortened the N1-C2-N21 bond angle increased.

Journal Article↗
PubMed2004

2-Acetamido-4-p-tolyl-1,3-thiazole and 2-amino-4-p-tolyl-1,3-thiazolium chloride dihydrate.

The structures of 2-acetamido-4-tolyl-1,3-thiazole, C(12)H(12)N(2)OS, (I), and 2-amino-4-tolyl-1,3-thiazolium chloride dihydrate, C(10)H(11)N(2)S(+).Cl(-).2H(2)O, (II), reveal that both molecules are essentially planar, with the respective dihedral angles between the benzene and thiazole rings being 2.9 (1) and 10.39 (7) degrees . Compound (I) associates via a single N-H...O interaction to form a flat alternate-facing hydrogen-bonded chain [graph-set C(2)(2)(4)]. Compound (II) packs with the hydrogen-bonding associations of the Cl atoms and the water molecules creating a convoluted hydrogen-bonded ribbon made up of five-membered donor-acceptor rings, involving three water O atoms (with associated H atoms) and two Cl atoms. The thiazolium rings form stacked columns, aligned in the same direction as the hydrogen-bonded ribbons, of alternate-facing molecules that are also involved in the hydrogen-bonding network, linking to the Cl atoms and one of the water molecules. Subsequently, each Cl atom is the hydrogen-bond acceptor for five separate O/N-H associations.

Journal Article↗
PubMed2004

2-Amino-2-thiazoline and its 1:1 organic salt with 2-naphthoxyacetic acid.

The crystal structures of 2-amino-2-thiazoline, C3H6N2S, and 2-amino-2-thiazolinium 2-naphthoxyacetate, C3H7N2S+.C12H9O3-, are reported. The structure of 2-amino-2-thiazoline consists of two unique molecules that construct a convoluted hydrogen-bonded ribbon involving R(2)2(8) graph-set association via both N-H...N and N-H...S interactions. The organic salt structure consists of the two molecules associated via an R(2)2(8) graph-set dimer through N-H...O interactions, with the hydrogen-bonding network propagated via additional N-H...O three-centre interactions from the second 2-amine H atom.

Antineoplastic Agents↗
PubMed2003

Four trifluoromethylnitrobenzene analogues.

The crystal structures of four trifluoromethylnitrobenzene analogues (CF(3))C(6)H(3)(NO(2))[C(4)H(8)N(2)]R (where C(4)H(8)N(2) is piperazinyl and R is ethyl carboxylate, CO(2)C(2)H(5), or phenyl, C(6)H(5)), have been determined, and their conformations and packing arrangements are compared. The four compounds are ethyl 4-[4-nitro-2-(trifluoromethyl)phenyl]piperazine-1-carboxylate, (I), and ethyl 4-[2-nitro-4-(trifluoromethyl)phenyl]piperazine-1-carboxylate, (II), both C(14)H(16)F(3)N(3)O(4), and 1-[4-nitro-2-(trifluoromethyl)phenyl]-4-phenylpiperazine, (III), and 1-[2-nitro-4-(trifluoromethyl)phenyl]-4-phenylpiperazine, (IV), both C(17)H(16)F(3)N(3)O(2). All molecules adopt a rod-like conformation, while the asymmetric units of (II) and (IV) contain two unique molecules that pack as monodirectional pairs. All molecules pack with C-H...O/F close contacts to all but one of the O atoms and to five of the 18 F atoms.

Journal Article↗
PubMed2003

2-Phenylmalonpiperadide and 2-phenylmalonmorpholide.

The structures of 2-phenylmalonpiperadide [systematic name: 2-phenyl-1,3-bis(piperidin-1-yl)propane-1,3-dione, C(19)H(26)N(2)O(2), (I)] and 2-phenylmalonmorpholide [systematic name: 1,3-dimorpholino-2-phenylpropane-1,3-dione, C(17)H(22)N(2)O(4), (II)], have been determined and both their molecular conformations and packing arrangements compared. Although chemically similar, compounds (I) and (II) exhibit different molecular conformations. The only general conformational similarities are that their respective carbonyl groups are orientated in the same direction and the heterocyclic rings exist in the chair arrangement. General similarities in the packing arrangements arise due to both compounds having the same space group (P2(1)2(1)2(1)) and a similar alignment of their phenyl-substituted backbone with respect to the c axis. Similar C-H.O hydrogen-bonding associations are listed for the carbonyl O atoms, while only one of the morpholine O atoms is involved in any such association.

Journal Article↗
PubMed2003

1-(4-chlorophenylsulfanyl)-2-nitro-4-(trifluoromethyl)benzene and 1-(4-chlorophenylsulfanyl)-4-nitro-2-(trifluoromethyl)benzene.

Two chemical isomers of 3-nitrobenzotrifluoride, namely 1-(4-chlorophenylsulfanyl)-2-nitro-4-(trifluoromethyl)benzene, C(13)H(7)ClF(3)NO(2)S, (I), and 1-(4-chlorophenylsulfanyl)-4-nitro-2-(trifluoromethyl)benzene, C(13)H(7)ClF(3)NO(2)S, (II), have been prepared and their crystal structures determined with the specific purpose of forming a cocrystal of the two. The two compounds display a similar conformation, with dihedral angles between the benzene rings of 83.1 (1) and 76.2 (1) degrees, respectively, but (I) packs in P-1 while (II) packs in P2(1)/c, with C-H.O interactions. No cocrystal could be formed, and it is suggested that the C-H.O associations in (II) prevent intermolecular mixing and promote phase separation.

Journal Article↗
PubMed2002

Three 2-aminopurine derivatives.

The structure of 2-amino-6-chloropurine, C(5)H(4)ClN(5), (I), comprises a flat molecule, with all possible strong hydrogen-bond donors and acceptors involved in the hydrogen-bonding network. The structures of 2-amino-6-(4-chlorophenylsulfanyl)purine hemihydrate, C(11)H(8)ClN(5)S.0.5H(2)O, (II), and 2-amino-6-(4-methylphenylsulfanyl)purine 0.33-hydrate, C(12)H(11)N(5)S.0.33H(2)O, (III), have two and three unique molecules, respectively, and one water molecule in their asymmetric units. Both (II) and (III) exhibit elaborate hydrogen-bonding networks that involve the S (for both) and Cl [for (II)] atoms in addition to the expected strong hydrogen-bonding sites. Both structures also have offset-stacking formations of the phenyl and purine rings.

2-Aminopurine↗
PubMed2002

2-(Pyrrolidin-1-yl)-1,4-naphthoquinone and 2-phenylsulfanyl-3-(pyrrolidin-1-yl)-1,4-naphthoquinone.

The structure of 2-(pyrrolidin-1-yl)-1,4-naphthoquinone, C(14)H(12.95)Cl(0.05)NO(2), (I), is actually a 0.95:0.05 mixture including 2-chloro-3-(pyrrolidin-1-yl)-1,4-naphthoquinone as a minor impurity, but (I) was resolved as a single molecule containing a Cl atom with 5% occupancy at the 3-position. Compound (I) was prepared from the fully chloro-substituted analogue in an attempt to produce the disubstituted pyrrolidinyl derivative. 2-Phenylsulfanyl-3-(pyrrolidin-1-yl)-1,4-naphthoquinone, C(20)H(17)NO(2)S, (II), was also prepared from 2-chloro-3-(pyrrolidin-1-yl)-1,4-naphthoquinone, using a strong exocyclic nucleophile. The structure of (II) differs from previous structures of 2,3-dichloro-1,4-naphthoquinone and its derivatives in that the naphthoquinone ring is non-planar.

Journal Article↗
PubMed2002

1-(2-Pyridyl) ethan-1-one 8-quinolylhydrazone and 1-(1H-pyrrol-2-yl) ethan-1-one 8-quinolylhydrazone.

The structures of the title compounds, C(16)H(14)N(4), (I), and C(15)H(14)N(4), (II), respectively, have been determined, and their molecular packing arrangements compared. Both are essentially flat molecules, with respective dihedral angles between the quinoline and heterocyclic rings of 19.0 (1) and 8.5 (2) degrees. The pyridyl derivative, (I), packs in a P2(1)/c unit cell, while in the pyrrolyl compound, (II), the molecules pack in Pca2(1) and form a crinkled ribbon arrangement through the association of pyrrole NH groups with the quinoline N atoms.

Journal Article↗