82 research outputs found
Organotin Compound Derived from 3-Hydroxy-2-formylpyridine Semicarbazone: Synthesis, Crystal Structure, and Antiproliferative Activity
The novel diphenyltin(IV) compound [Ph2(HyFoSc)Sn] (2), where H2HyFoSc (1) is 3-hydroxy-2-formylpyridine semicarbazone, was prepared and characterized by vibrational and NMR (1H, 13C) spectroscopy. The structure of [Ph2(HyFoSc)Sn] was confirmed by single-crystal X-ray crystallography. The doubly deprotonated ligand is coordinated to the tin atom through the enolic-oxygen, the azomethine-nitrogen, and phenolic-oxygen, and so acts as an anionic tridentate ligand with the ONO donors. Two carbon atoms complete the fivefold coordination at the tin(IV) center. Intermolecular hydrogen bonding, C–H → π, and π → π interactions combine to stabilize the crystal structure. Compounds 1 and 2 have been evaluated for antiproliferative activity in vitro against the cells of three human tumor cell lines: MCF-7 (human breast cancer cell line), T24 (bladder cancer cell line), A549 (nonsmall cell lung carcinoma), and a mouse fibroblast L-929 cancer cell line
(±)-Cyclohexane-1,2-diyl bis(4-nitrobenzoate)
The crystal structure of the title compound, C20H18N2O8, has been investigated to establish the relative stereochemistry between the ester groups. The cyclohexane ring adopts a chair conformation, in which the two ester groups occupy the adjacent equatorial positions in a trans relationship with each other. The molecules assemble in the crystal as chains along the c axis via C—H⋯π interactions between the cyclohexane ring and a pair of nitrophenyl rings of the neighbouring molecule. Also observed are π–π stacking interactions between the nitrophenyl rings of neighbouring chains, with a perpendicular distance between these rings of 3.409 Å and a slippage of 0.969 Å
ChemInform Abstract: Synthesis of O-Methyl S-(3,4,6-Tri-O-acetyl-2-deoxy-α-D-arabino-hexopyranosyl) (R)-Dithiophosphate Ion and the X-Ray Crystal Structures of the Dipropylammonium Salt.
ChemInform Abstract: CONFORMATIONAL ANALYSIS OF DOUBLE CARBOXYLIC BRIDGES IN BIS(DL-α-ALANINE)MANGANESE(II) DIBROMIDE DIHYDRATE AND THE RELATED COMPOUNDS
ChemInform Abstract: Methyl 2,4-Dideoxy-6,7,8,9,10-penta-O-acetyl-D-glycero-α-D-gluco- decapyranosid-3-ulose.
ChemInform Abstract: Synthesis and Crystal Structure of 6,6′-Dichloro-6,6′-dideoxy-2,3,4,3′ 4′-penta-O-benzylsucrose.
Stable Hemiaminals: 2-Aminopyrimidine Derivatives
Stable hemiaminals can be obtained in the one-pot reaction between 2-aminopyrimidine and nitrobenzaldehyde derivatives. Ten new hemiaminals have been obtained, six of them in crystal state. The molecular stability of these intermediates results from the presence of both electron-withdrawing nitro groups as substituents on the phenyl ring and pyrimidine ring, so no further stabilisation by intramolecular interaction is required. Hemiaminal molecules possess a tetrahedral carbon atom constituting a stereogenic centre. As the result of crystallisation in centrosymmetric space groups both enantiomers are present in the crystal structure
The DFT study on the reaction between benzaldehyde and 4-amine-4H-1,2,4-triazole and their derivatives as a source of stable hemiaminals and schiff bases. Effect of substitution and solvation on the reaction mechanism
Reaction mechanism for the benzaldehyde (ald) and 4-amine-4H-1,2,4-triazole (4at) has been investigated at the DFT (B3LYP)/6–31+G(d) computational level. Three transition states (TS) have been identified. The TS1 corresponds to hydrogen transfer from the NH2 group to the C = O bond and nucleophillic attack of the carbon atom from the aldehyde group on the nitrogen atom from the NH2 group in 4at. The result of this reaction is the hemiaminal molecule. The TS2 characterises an internal rearrangement of the benzene and triazole rings in the hemiaminal molecule. The TS3 leads to breaking of the O-H bond, the elimination reaction of the H2O molecule, and formation of the C=N bond. The final product of this reaction is a Schiff base. In order to determine the most favorable conditions for hemiaminal formation, the influence of electronic structure modification on the energetic properties during the reaction of benzaldehyde and 4-amine-4H-1,2,4-triazole has been studied. Thirteen substituents: NH2, OH, OCH3, CH3, F, I, Cl, Br, COH, COOH, CF3, CN, NO2, with different Hammett’s constant values (σ = −0.66–+0.78) have been considered. Finally, the reaction mechanism has been investigated in the presence of 1 to 5 water molecules
Why Is the Resolution of Certain Racemic Modifications Inefficient? Formation of Diastereomeric Double Salts of Brucinium
Fractional crystallization of diastereomeric salts remains
the
most frequently used method for a separation of racemic compounds,
and yet it has been performed by trial and error. For a better understanding
of the chiral discrimination mechanism that is useful for the rationalization
of optical resolution and help in choosing the crucial experimental
parameters, structural investigations of products of both successful
and unsuccessful racemic resolution are important. The former and
the latter typically involve diastereomeric salts precipitating fractionally
and the formation of solid solutions of diastereomeric salts or diastereomeric
double salts, respectively. In this contribution, a mechanism of recognition
leading to formation of the diastereomeric double salts is proposed
based on crystal structures of three brucinium double salts (bis(brucinium) <i>N</i>-(3,5-dinitrobenzoyl)-dl-alaninate methanol 3-solvate,
bis(brucinium) <i>N</i>-(3,5-dinitrobenzoyl)-dl-alaninate 5.75-hydrate, and bis(brucinium) <i>N</i>-(3,5-dinitrobenzoyl)-dl-serinate 0.10-hydrate) as well as of some relevant diastereomeric
salts (containing the d- or l-enantiomer of the
alanine or the serine derivative)
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