5-Endo-trig cyclizations are generally considered to be kinetically unfavourable, as described by Baldwin's rules. Consequently, observation of this mode of reaction under kinetic control is rare. This is usually ascribed to challenges in achieving appropriate approach trajectories for orbital overlap in the transition state. Here, we describe a highly enantio- and diastereoselective route to c...

A set of hypotheses is proposed that explains the anomeric specificity of aldopyranose dehydrogenases in terms of an evolutionarily selected function. The first hypothesis, based on stereoelectronic theory, argues that, in the "allowed" transition state for oxidation at the anomeric carbon, the two oxygens attached to the anomeric carbon each bear a lone pair of electrons antiperiplanar to the ...

Objective(s): Vinblastine is antimitotic, anticancer medicine that disturbs normal microtubule formation and favours depolymerisation. Structural study and finding the active site of vinblastine are the targets of this research.   Materials and Methods: Vinblastine was optimized in vacuum and then in different solvents by Density Functional Theory (DFT) method. Nuclear Magnetic Resonance (NMR) ...

A classic question regarding hydrogen bonds (H-bonds) concerns their symmetry. Is the hydrogen centered or is it closer to one donor and jumping between them? These possibilities correspond to singleand double-well potentials, respectively. The NMR method of isotopic perturbation can answer this question. It is illustrated with 3-hydroxy-2-phenylpropenal and then applied to dicarboxylate monoan...

objective(s): vinblastine is antimitotic, anticancer medicine that disturbs normal microtubule formation and favours depolymerisation. structural study and finding the active site of vinblastine are the targets of this research.   materials and methods: vinblastine was optimized in vacuum and then in different solvents by density functional theory (dft) method. nuclear magnetic resonance (nmr) ...

Thermodynamic electron-transfer potentials from biology textbooks elucidate the sequence of electron-transfer events in the respiratory chain in mitochondria. In this study, thermodynamic and kinetic oxygen-transfer potentials have been defined and predicted for oxidants and substrates using density functional theory, aiming to rationalize multiple oxygen-transfer events in chemical catalysis, ...

The facial selectivity of double Michael addition reactions of the silylated Nazarov reagent 4 to unsaturated indolo[2,3-a]quinolizidine lactams 3 has been studied. Pentacyclic 3-H/15-H trans adducts 5 are generated from Nind -unsubstituted lactams, but the corresponding cis isomers 6 are formed when the indole nitrogen has a tert-butyloxycarbonyl (Boc) substituent. This reversal in the facial ...

We introduce a previously unexplored parameter-halenium affinity (HalA)- as a quantitative descriptor of the bond strengths of various functional groups to halenium ions. The HalA scale ranks potential halenium ion acceptors based on their ability to stabilize a "free halenium ion". Alkenes in particular but other Lewis bases as well, such as amines, amides, carbonyls, and ether oxygen atoms, e...