Two possible isomers of some 1,3-diaryl-H-benzo[f]chromene have been studied using density functional theory. Structures of E1 and E2 isomers were optimized at the B3LYP and MP2 levels with different basis sets. The total electronic energies show that E2 isomer is about 3-5 kcal/mol more stable than E1 isomer and this energy difference is attributed to the planarity of heterocyclic ring and mor...

Vinyl cyclopropane rearrangement (VCPR) has been utilised to synthesise a difluorinated cyclopentene stereospecifically and under mild thermal conditions. Difluorocyclopropanation chemistry afforded ethyl 3-(1'(2'2'-difluoro-3'-phenyl)cyclopropyl) propenoate as all four stereoisomers (18a, 18b, 22a, 22b) (all racemic). The trans-E isomer (18a), prepared in 70 % yield over three steps, underwent...

The thermal conversion of cis-bicyclo[4.2.0]oct-7-ene to cis,cis-1,3-cyclooctadiene might involve a direct disrotatory ring opening, or it might possibly take place by way of cis,trans-1,3-cyclooctadiene. This cis,trans-diene might possibly form the more stable cis,cis isomer through a [1,5] hydrogen shift or a trans-to-cis isomerization about the trans double bond. Deuterium kinetic isotope ef...

Among the four possible stereoisomers of 3,4-dihydroxy-L-proline,2,3-trans-3,4-trans-3,4-dihydroxy-L-proline (IV) had not been found in nature previously. It has now been detected as a component of virotoxins, toxic peptides of Amanita virosa mushrooms. Because periodate failed to effect an oxidative glycol splitting reaction, the two hydroxyl groups in positions 3 and 4 were expected to be in ...

Azobenzene and its derivatives can undergo reversible trans-cis isomerizations when irradiated with light, making them potential candidates for optically sensitive materials and devices. The adsorption and diffusion of azobenzene on the Cu(110) surface was investigated with a variable-temperature scanning tunneling microscope. The trans-isomer was observed and found to occupy two adsorption geo...

Ab initio quantum chemical and free energy molecular dynamics calculations are performed to examine energy differences between the all-trans and (13,15)cis conformers of retinal, i.e., those populated in the dark-adapted state of bacteriorhodopsin. The quantum chemical results are used to derive an empirical force field that is used to calculate an adiabatic potential energy map for rotation ab...

Both cis-diamminedichloroplatinum(II) (cisplatin or cis-DDP) and trans-diamminedichloroplatinum(II) form covalent adducts with DNA. However, only the cis isomer is a potent anticancer agent. It has been postulated that the selective action of cis-DDP occurs through specific binding of nuclear proteins to cis-DDP-damaged DNA sites and that binding blocks DNA repair. We find that a very abundant ...

Both enantiomers of trans-cyclohexane-1,2-diammonium sulfate and trans-1,2-diphenylethylenediammonium sulfate were used as "tailor-made" additives to direct the mirror-symmetry breaking in the attrition-enhanced deracemization (i.e. Viedma ripening) of conglomerate crystals of ethylenediammonium sulfate (EDS). Isothermal titration calorimetry (ITC) shows chiral recognition of (1R,2R)- and (1S,2...

For the CH3CHOO Criegee intermediates (ethanal-oxide) and analogous anions, we obtain heats of formations and electron affinities at CCSDT(Q)/CBS level of theory by means of the high-level W3-F12 thermochemical protocol. The electron affinities amount to 0.20 eV and 0.35 eV for the cis and trans isomer, respectively. Neutral cis and trans isomers are separated by 14.1 kJmol−1, the anions are al...

An azobenzene-capped DNA hairpin coupled to an AFM is presented as an optically triggered single-molecule motor. The photoinduced trans to cis isomerization of azobenzene affects both the overall length of the molecule and the ability of the DNA bases to hybridize. Using a combination of molecular dynamics simulations and free energy calculations the unfolding of both isomers along the O5'-O3' ...