Chemo-, regio- and enantioselective hydroformylation of trisubstituted cyclopropenes: access to chiral quaternary cyclopropanes.

Catalytic asymmetric synthesis of polysubstituted chiral cyclopropane presents a significant challenge in organic synthesis due to the difficulty in enantioselective control. Here we report a rhodium-catalyzed highly chemo-, regio- and enantioselective hydroformylation of trisubstituted cyclopropenes affording chiral quaternary cyclopropanes. Importantly, the easy made sterically bulky ligand L1 can effectively suppress hydrogenation and decomposition reactions and give quaternary cyclopropanes with high regio- and enantioselectivities for both aryl and alkyl functionalized substrates.

Antioxidant activity of caffeic acid: thermodynamic and kinetic aspects on the oxidative degradation pathway.

Caffeic acid is a phenolic secondary metabolite from plants, which is known for its antioxidant properties. The effective mitigation of methanol-induced oxidative stress by caffeic acid depends on the direct radical scavenging as well as the formation of new metabolites oxidative degradation. Herein, thermodynamic and kinetic aspects of the oxidative degradation pathway of caffeic acid in the presence of radical CHO and its isomer, CHOH are discussed for the first time, employing density functional theory (DFT).

Curcumin analogues with improved antioxidant properties: A theoretical exploration.

Curcumin, a ubiquitous dietary molecule, is a versatile antioxidant that fights against free radicals. The antioxidant activity of curcumin and its structural analogues such as hispolon, halfcurcumin and polyhydroxycurcumin is analyzed using density functional theory (DFT). The thermochemical parameter, bond dissociation enthalpy (BDE) is used to analyse the propensity of radical attack.

Hydroxyl radical scavenging activity of melatonin and its related indolamines.

The hydroxyl radical (•OH) scavenging activities of Melatonin, an endogenously produced neurohormone and its related indolamines like -acetyl tryptophan (NAT) and -acetyl serotonin (NAS) have been investigated using density functional theory. The mechanism involves 4 steps: initial radical addition to position-3 of the indole ring, keto-amine to enol-imine tautomerization, cyclisation, and finally, addition of a second •OH leading to a cyclic end product. Incorporation of an explicit water molecule in tautomerization step leads to a significant reduction in the barrier of this step, so that the subsequent cyclisation step becomes rate-limiting.