Camila Botin Francisco

A metal-free lactamisation/ N -acyliminium cyclisation cascade enables rapid access to functionalised indolizino[8,7- b ]indoles with high diastereoselectivity.

Fluorine NMR is a highly sensitive technique for delineating the conformational states of biomolecules and has shown great utility in drug screening and in understanding protein function. Current fluorinated protein tags leverage the intrinsic chemical shift sensitivity of the ¹⁹F nucleus to detect subtle changes in protein conformation and topology. This chemical shift sensitivity can be amplified by embedding the fluorine or trifluoromethyl reporter within a pyridone. Due to their polarizability and rapid tautomerization, pyridones exhibit a greater range of electron delocalization and correspondingly greater ¹⁹F NMR chemical shift dispersion. To assess the chemical shift sensitivity of these tautomeric probes to the local environment, ¹⁹F NMR spectra of all possible monofluorinated and trifluoromethyl-tagged versions of 2-pyridone were recorded in methanol/water mixtures ranging from 100% methanol to 100% water. 4-Fluoro-2-pyridone and 6-(trifluoromethyl)-2-pyridone (6-TFP) displayed the greatest sensitivity of the monofluorinated and trifluoromethylated pyridones, exceeding that of known conventional CF₃ reporters. To evaluate the utility of tautomeric pyridone tags for ¹⁹F NMR of biomolecules, the alpha subunit of the stimulatory G protein (G_sα) and human serum albumin (HSA) were each labeled with a thiol-reactive derivative of 6-TFP and the spectra were recorded as a function of various adjuvants and drugs. The tautomeric tag outperformed the conventional tag, 2-bromo-N-(4-(trifluoromethyl)phenyl)acetamide through the improved resolution of several functional states.

Este trabalho teve o objetivo avaliar o efeito da aplicação de revestimentos comestíveis a base de amido e caseína sobre as características físico-químicas de goiabas. Os tratamentos utilizados foram: Testemunha (sem aplicação); A (revestimento de amido); AC (revestimento de amido + caseína); C (revestimento de caseína). As goiabas foram analisadas em relação à perda de massa, acidez total titulável, sólidos solúveis totais, vitamina C e colorimetria. O revestimento comestível de amido (A) obteve menor perda de massa (10,65%). As goiabas com revestimento de amido (A) e caseína (C) conservaram os teores iniciais de sólidos solúveis totais. Todos os revestimentos comestíveis foram eficientes na conservação de ATT. O tratamento AC obteve menor amarelecimento das goiabas.

The presence of strong stereoelectronic interactions involving the substituents in cis-2-substituted cyclohexanes may lead to results different from those expected. In this work, we studied the conformational behavior of cis-2-fluoro- (F), cis-2-chloro- (Cl), cis-2-bromo- (Br) and cis-2-iodocyclohexylamine (I) by dynamic NMR and theoretical calculations. The experimental data pointed to an equilibrium strongly shifted toward the ea conformer (equatorial amine group and axial halogen), with populations greater than 90% for F, Cl and Br in both dichloromethane-d₂ and methanol-d₄. Theoretical calculations (M06-2X/6-311++G(2df,2p)) were in agreement with the experimental, with no influence of the solvent or the halogen on the equilibrium. A principal component analysis of natural bond orbital energies pointed to the σ*_C–X and σ_C–H orbitals and the halogen lone pairs (LP_X) as the most significant for the hyperconjugative interactions that influenced the equilibrium. The σ_C–H → σ*_C–X hyperconjugation and the interactions involving the LP_X counterbalance each other, explaining the non-influence of the halogen on the conformational equilibrium. These interactions are responsible for the strong preference for the ea conformer in cis-2-halocyclohexylamines, being strong enough to restrain the shift in the equilibrium due to other factors such as steric repulsion or solvent effects.