High regioselectivity in the amination reaction of isoquinolinequinone derivatives using conceptual DFT and NCI analysis.

DFT-derived reactivity descriptors and Non-Covalent interaction (NCI) analysis were performed to rationalize the regioselectivity in the amination reaction of some isoquinolinequinone derivatives. Statistical analysis was performed to assess robustness of atomic charges to the basis set. Various electronic population schemes including Mulliken population analysis (MPA), electrostatic method (ChelpG), Hirshfeld population analysis (HPA) and Natural population analysis (NPA) have been considered. The results revealed that NPA was the most efficient for this purpose. NCI study using the reduced density gradient (RDG) was performed for revealing weak interactions. Domains defined by isosurfaces of RDG have been integrated to quantitatively study the strength of weak interactions and their stabilities have also been examined. Steric hindrance caused by coordination of ethanol with the neighboring carbonyl prevents the nucleophilic attack on C-6 and therefore leads to preferential C-7 substitution. The quantitative study of NCI clearly demonstrates that the hydrogen bond of carbonyl (2) is more stabilizing. Consequently, the high polarity of hydrogen bond on this carbonyl may explain the high electrophilicity of C-5 compared to C-8. Our work proved that the difference in local reactivity, as well as the steric hindrance are the key elements explaining the high regioselectivity exhibited by the amination reaction.

In vivo quantitative NMR imaging of fruit tissues during growth using Spoiled Gradient Echo sequence.

Nondestructive studies of physiological processes in agronomic products require increasingly higher spatial and temporal resolutions. Nuclear Magnetic Resonance (NMR) imaging is a non-invasive technique providing physiological and morphological information on biological tissues. The aim of this study was to design a robust and accurate quantitative measurement method based on NMR imaging combined with contrast agent (CA) for mapping and quantifying water transport in growing cherry tomato fruits. A multiple flip-angle Spoiled Gradient Echo (SGE) imaging sequence was used to evaluate the intrinsic parameters maps M0 and T1 of the fruit tissues. Water transport and paths flow were monitored using Gd(3+)/[Fe(CN)6](3-)/D-mannitol nanoparticles as a tracer. This dynamic study was carried out using a compartmental modeling. The CA was preferentially accumulated in the surrounding tissues of columella and in the seed envelopes. The total quantities and the average volume flow of water estimated are: 198 mg, 1.76 mm(3)/h for the columella and 326 mg, 2.91 mm(3)/h for the seed envelopes. We demonstrate in this paper that the NMR imaging technique coupled with efficient and biocompatible CA in physiological medium has the potential to become a major tool in plant physiology research.