Ascorbic acid (vitamin C) has been used as a radical initiator in a metal‐free direct CH arylation of (hetero)arenes. Starting from an aniline, the corresponding arenediazonium ion is generated in ...situ and immediately reduced by vitamin C to an aryl radical that undergoes a homolytic aromatic substitution with a (hetero)arene. Notably, neither heating nor irradiation is required. This procedure is mild, operationally simple, and constitutes a greener approach to arylation.
Vitamin C oupling: A catalytic amount of ascorbic acid acted as a radical initiator in a metal‐free direct CH arylation of arenes and heteroarenes with anilines (see scheme; Boc=tert‐butoxycarbonyl). The reaction requires no heating or irradiation, is operationally simple, and constitutes a greener approach to arylation.
Directional bonding strategies guide the design of complex molecular architectures, yet challenges arise due to emergent behavior. Rigid structures face geometric constraints and sensitivity to ...mismatches, hindering the efficient assembly of molecular organic cages (MOCs). Harnessing intramolecular non‐covalent interactions offers a promising solution, broadening geometrical possibilities and enhancing adaptability to boost assembly yields. However, identifying these interactions remains challenging, with their full potential sometimes latent until final assembly. This study explores these challenges by synthesizing boronic acid tripods with varied oxygen positions at the tripodal feet and investigating their role in assembling tetrahedral boronate MOCs. Our results reveal substantial differences in the assembly efficiency among tripods. While the building blocks with oxygen in the benzylic position relative to the central aromatic ring form the MOCs in high yields, those with the oxygen atom directly bound to the central aromatic ring, only yield traces. Through X‐ray crystallography and DFT analyses, we elucidate how intramolecular interactions profoundly influence the geometry of the building blocks and cages in a relay‐like fashion, highlighting the importance of considering intramolecular interactions in the rational design of (supra)molecular architectures.
Latent intramolecular non‐covalent interactions (NCIs) within the building blocks play a crucial role in the assembly of molecular organic cages (MOCs) via Dynamic Covalent Chemistry (DCC). These intramolecular interactions emerge from induced conformational restrictions during cage assembly, ultimately dictating the reaction outcome in a relay‐like fashion.
The discovery of molecular organic cages (MOCs) is inhibited by the limited organic-chemical space of the building blocks designed to fulfill strict geometric requirements for efficient assembly. ...Using intramolecular attractive or repulsive non-covalent interactions to control the conformation of flexible systems can effectively augment the variety of building blocks, ultimately facilitating the exploration of new MOCs. In this study, we introduce a set of boronic acid tripods that were designed using rational design principles. Conformational control was induced by extending the tripod's arms by a 2,3-dimethylbenzene unit, leading to the efficient formation of a tetrapodal nanometer-sized boroxine cage. The new building block's versatility was demonstrated by performing cage metamorphosis upon adding an aromatic tetraol. This led to a quantitative boroxine-to-boronate transformation and a topological shift from tetrahedral to trigonal bipyramidal.
The conformational control of boronic acid building blocks allows efficient self-assembly into a tetrahedral boroxine cage. The nano-sized cage displays molecular metamorphosis, converting from a boroxine tetrapod to a boronate bipyramid.
•ONS contributes to increase energy, protein and nutrients in cancer patients.•Enhanced ONS increases the intake in cancer patients in worse clinical conditions.•Enhanced ONS for cancer had a high ...adherence, good tolerance, and acceptance.
Display omitted
The aim of this study was to evaluate the impact of an enhanced ONS (enriched in EPA, DHA, leucine, and beta-glucans) on the dietary intake of cancer patients.
A randomized, double-blind, parallel, controlled, and multicenter clinical trial was conducted in patients with cancer and malnutrition. The trial compared prescribed dietary advice and two packs per day, for 8 weeks, of a hypercaloric (400 kcal/pack) and hyperproteic ONS (20 g/pack) with fiber and specific ingredients (leucine, EPA and DHA, and beta-glucans) (enhanced-ONS) versus an isocaloric and isoproteic formula (standard-ONS) without specific ingredients. Food intake was assessed with a 3-day dietary survey, and adherence to the supplement with a patient self-completed diary.
Thirty-seven patients completed the intervention period. The combined intervention of dietary advice and ONS managed to increase the energy intake of the overall cohort by 792.55 (378.57) kcal/day, protein by 40.72 (19.56) g/day. Increases in energy and nutrient intakes were observed in both groups, both in dietary intake and associated exclusively with the supplement. The group that received the enhanced-ONS ingested a greater volume of product when there was a greater severity of malnutrition; a tumor location in the head, neck, upper digestive area, liver, or pancreas; more advanced stages of the tumor; or the receipt of more than one antineoplastic treatment.
The use of an enhanced-ONS helps meet the nutritional requirements of cancer patients, especially those who have a more compromised clinical condition, with high adherence, good tolerance, and acceptance.
Cyclic products can be obtained through the intramolecular version of the Nicholas reaction, which requires having the nucleophile connected to the alkyne unit. Here, we report the synthesis of ...1-oxa-3-cyclooctynes starting from commercially available (1
,3
)-camphoric acid. The strategy is based on the initial preparation of propargylic alcohols, complexation of the triple bond with Co
(CO)
, and treatment with BF
·Et
O to induce an intramolecular Nicholas reaction with the free hydroxyl group as nucleophile. Finally, oxidative deprotection of the alkyne afforded the cyclooctynes in good yields. Notably, large-sized R substituents at the chiral center connected to the O atom were oriented in such a way that steric interactions were minimized in the cyclization, allowing the formation of cyclooctynes exclusively with
configuration, in good agreement with theoretical predictions. Moreover, preliminary studies demonstrated that these cyclooctynes were reactive in the presence of azides yielding substituted triazoles.
Honey samples (n = 126) from Castilla-La Mancha (Central Spain) were characterized based on their physicochemical properties and a melissopalynological analysis. The latter showed that Echium pollen ...type was the dominant palynomorph in most samples, representing at least 30% of the pollen in each sample. As anticipated, a relationship was observed between the proportion of this pollen and the properties of the honey. One goal of this study was to set a threshold that defines the percentage of pollen necessary for Viper's bugloss honey to be considered monofloral or multifloral. This is a mandatory requirement in light of the publication of the European Directive 2014/63/EU establishing the regulations governing the labelling and control of honey to eradicate fraud (BOE n° 147, June 2015). By analyzing how the proportions of Echium pollen type affected the physicochemical and sensory parameters of the honey, the honeys analyzed could be segregated into multifloral and monofloral honeys. The data indicates that the proportion of pollen necessary to discriminate monofloral Viper's bugloss honey lies at 70%.
Call in the reinforcements: Intra‐receptor noncovalent interactions can enantioselectively cooperate with guest binding, thus triggering chiral discrimination. Such cooperativity is described and ...quantified for a simple synthetic system wherein an intra‐receptor hydrogen bond cooperates with a CH–π interaction exclusively formed with the D enantiomer of the guest, thus exemplifying reinforced chiral recognition (see picture).
Positive cooperativity between host conformational equilibria and guest binding has been widely reported in protein receptors. However, reported examples of this kind of cooperativity in synthetic ...hosts are scarce and largely serendipitous, among other things because it is hard to envision systems which display this kind of cooperativity. In order to shed some light on the correlation between conformational equilibria of free host and guest binding, selected structural modifications have been performed over a family of nonpreorganized hosts in order to induce conformational changes and to analyze their effect on the binding affinity. The conformational effect was evaluated by a theoretical conformational search and correlated with the ability of the receptors. All data suggest that those receptors that display the best association constants are able to sample folded conformations analogous to the conformational requirements for the binding of the guests. On the contrary, for those receptors where folded conformers are scarce, then the association constant and enantioselectivity clearly drop.
PDF
