Synthesis of dispiro-orthoester an acetal oxo-carbenium ion.

The first dispiro orthoester a spiroacetal oxo-carbenium ion is presented. Oxidative dearomatization of phloretic esters results in a bifunctional electrophilic spiroacetal oxo-carbenium ion, which undergoes a double nucleophilic addition by diol delivering a range of unusual dispiro-orthoesters with an excellent diversity.

Comparison of four digestion protocols on the physical characteristics of gastric digesta from cooked couscous using the Human Gastric Simulator.

digestion is widely employed in food, nutraceutical and pharmaceutical research, and numerous gastric digestion protocols have been proposed, with a wide range of experimental conditions. Differences in the simulated gastric fluids (pH, mineral content, enzyme type and enzyme activity) of different digestion protocols may alter the results for the digestion of the same meal. This study aimed to investigate how variations in the gastric secretion rate and composition in four digestion protocols (Infogest Riddet, Infogest Semi-dynamic, UC Davis and United States Pharmacopeia) impacted the physical properties of the emptied gastric digesta.

Iso-Pentadienyl Carbonate as a Five Carbon Synthon in Manganese(I)-Catalyzed Selective Linear 1,3-Dienylation.

Selective linear 1,3-dienylations are essential transformations, and numerous synthetic efforts have been documented. However, a general method enabling access to electron-rich, -poor, and biologically relevant dienyl molecules is in high demand. Hence, we report a straightforward method of manganese(I)-catalyzed C-H dienylation of arenes by using iso-pentadienyl carbonate as a five carbon synthon.

Robust Synthesis of Terpenoid Scaffolds under Mn(I)-Catalysis.

The 6/6/5-fused tricyclic scaffold is a central feature of structurally complex terpenoid natural products. A step-economical cascade transformation that leads to a complex molecular skeleton is regarded as a sustainable methodology. Therefore, we report the first Mn(I)-catalyzed C(sp)-H chemoselective dienylation and diastereoselective intramolecular Diels-Alder reaction using -pentadienyl carbonate to access 6/6/5-fused tricyclic scaffolds.

Cooked Rice-Based and Wheat-Based Food Structure Influenced Digestion Kinetics and Glycemic Response in Growing Pigs.

Background: How starch-based food structure can affect the rate and extent of digestion in the small intestine and resulting glycemic response is not properly understood. One possible explanation is that food structure influences gastric digestion, which subsequently determines digestion kinetics in the small intestine and glucose absorption. However, this possibility has not been investigated in detail.

Influence of food macrostructure on the kinetics of acidification in the pig stomach after the consumption of rice- and wheat-based foods: Implications for starch hydrolysis and starch emptying rate.

How the stomach can serve as a biochemical environment for starch digestion and the implications on starch emptying are not well-understood. Biochemical changes during gastric digestion of cooked wheat- and rice-based diets of varying particle size and microstructure were investigated using a growing pig model. In larger-particle size diets (rice grain, rice noodle, pasta), pH >3 was maintained in the proximal stomach digesta even until 240 min digestion, resulting in extended remaining amylase activity and accumulation of maltose from starch hydrolysis in the stomach.

Lipid-Based Nanocarrier System for the Effective Delivery of Nutraceuticals.

Nutraceuticals possess several health benefits and functions; however, most nutraceuticals are prone to degradation in the gastrointestinal environment and have poor bioavailability. Application of a novel carrier system is of increasing importance to overcome obstacles and provide efficient applicability. Lipid-based nanocarriers provide a large surface-to-mass ratio, enhanced intestinal absorption by solubilization in the intestinal milieu, intestinal lymphatic transport, and altering enterocyte-based transport.

Mucoadhesive Delivery System: A Smart Way to Improve Bioavailability of Nutraceuticals.

The conventional oral administration of many nutraceuticals exhibits poor oral bioavailability due to the harsh gastric conditions and first-pass metabolism. Oral mucosa has been recognized as a potential site for the delivery of therapeutic compounds. The mucoadhesive formulation can adhere to the mucosal membrane through various interaction mechanisms and enhance the retention and permeability of bioactive compounds.

Correction: Tracking physical breakdown of rice- and wheat-based foods with varying structures during gastric digestion and its influence on gastric emptying in a growing pig model.

Correction for 'Tracking physical breakdown of rice- and wheat-based foods with varying structures during gastric digestion and its influence on gastric emptying in a growing pig model' by Joanna Nadia et al., Food Funct., 2021, DOI: 10.

Tracking physical breakdown of rice- and wheat-based foods with varying structures during gastric digestion and its influence on gastric emptying in a growing pig model.

There is currently a limited understanding of the effect of food structure on physical breakdown and gastric emptying of solid starch-based foods during gastric digestion. Moisture uptake, pH, particle size, rheological, and textural properties of six solid starch-based diets from different sources (Durum wheat and high amylose white rice) and of different macrostructures (porridge, native grain, agglomerate/couscous, and noodle) were monitored during 240 min of gastric digestion in a growing pig model. Changes in the physical properties of the gastric digesta were attributed to the influence of gastric secretions and gastric emptying, which were both dependent on the buffering capacity and initial macrostructure of the diets.

Streamlined Symmetrical Total Synthesis of Disorazole B and Design, Synthesis, and Biological Investigation of Disorazole Analogues.

Taking advantage of the -symmetry of the antitumor naturally occurring disorazole B molecule, a symmetrical total synthesis was devised with a monomeric advanced intermediate as the key building block, whose three-step conversion to the natural product allowed for an expeditious entry to this family of compounds. Application of the developed synthetic strategies and methods provided a series of designed analogues of disorazole B, whose biological evaluation led to the identification of a number of potent antitumor agents and the first structure-activity relationships (SARs) within this class of compounds. Specifically, the substitutions of the epoxide units and lactone moieties with cyclopropyl and lactam structural motifs, respectively, were found to be tolerable for biological activities and beneficial with regard to chemical stability.

Serendipitous Synthesis of Pyridoquinazolinones an Oxidative C-C Bond Cleavage.

A direct one-pot copper-catalyzed oxidative C-C bond cleavage route to the synthesis of pyridoquinazolinones is described. This one-pot strategy involves a copper-catalyzed C-N coupling followed by concomitant C(sp)-H oxidation and amidation oxidative C-C bond cleavage under an O atmosphere to deliver the target molecules in high yields.

Glycopeptides by Linch-Pin C-H Activations for Peptide-Carbohydrate Conjugation by Manganese(I)-Catalysis.

Late-stage C-H glycosylations of structurally complex amino acids and peptides were accomplished by means of racemization-free manganese(I)-catalyzed C-H activation. Thus, glycosylative modifications proved to be viable by a linch-pin approach, featuring chemo- and site-selective C-H transformations. The peptide-saccharide conjugation provided modular access to structurally complex glycopeptides, likewise enabling the assembly of fluorescent-labelled glycopeptides.

Copper Catalyzed Oxidative C-C Bond Cleavage of 1,2-Diketones: A Divergent Approach to 1,8-Naphthalimides, Biphenyl-2,2'-dicarboxamides, and N-Heterocyclic Amides.

We report here a simple and efficient copper catalyzed oxidative C-C bond cleavage of stable aromatic cyclic-fused and acyclic 1,2-diketones to deliver amides and imides in high yields. This newly developed protocol provides an excellent tool to transform structurally different 1,2-diketones into different products under the same reaction conditions. The key synthetic features of this methodology are the formation of 1,8-naphthalimides and biphenyl-2,2'-dicarboxamide motifs in high yields.

Syntheses of Cyclopropyl Analogues of Disorazoles A and B and Their Thiazole Counterparts.

Modular syntheses of disorazoles A and B analogues in which the epoxide moieties of the natural products were replaced with cyclopropyl units have been achieved. Targeted as part of a structure-activity relationships study, these syntheses were successfully extended to the thiazole counterparts of these analogues. The retrosynthetically defined fragments were assembled through Yamaguchi esterification, Cu/Pd-catalyzed cross-coupling, Yamaguchi macrolactonization, and Cu-catalyzed cross-coupling as the key reactions.

Transition-Metal-Free Multicomponent Approach to Stereoenriched Cyclopentyl-isoxazoles through C-C Bond Cleavage.

An efficient multicomponent reaction for the synthesis of stereoenriched cyclopentyl-isoxazoles from camphor-derived α-oximes, alkynes, and MeOH is reported. Our method involved a series of cascade transformations, including the in situ generation of an I catalyst, which catalyzed the addition of MeOH to a sterically hindered ketone. Oxidation of the oxime, and rearrangement of the α-hydroxyiminium ion generated a nitrile oxide in situ, which, upon [3+2] cycloaddition reaction with an alkyne, delivered the regioselective product.

Stereoselective Ring-Opening of gem-Difluorocyclopropanes: An Entry to Stereo-defined (E,E)- and (E,Z)-Conjugated Fluorodienes.

The ring-opening of gem-difluorocyclopropyl acetaldehydes producing selectively (E,E)- and (E,Z)-conjugated fluorodienals is described. Two stereo-divergent methods are presented to access both stereoisomers from a common precursor, in high yield and selectivity. The mechanistic aspect of these transformations is discussed.

Copper-Catalyzed Cascade Amination Route to N-Aryl Benzimidazoquinazolinones.

An efficient one-pot Cu-catalyzed C-H functionalization/two-fold C-N bond formation protocol for the syntheses of N-aryl benzimidazoquinazolinones is being reported. This strategy involves a Cu-catalyzed C-N bond coupling reaction between N-anilinoquinazolinones and aryl/heteroaryl halides followed by acetate ligand-assisted intramolecular C-H amination.a This reaction is high-yielding and straightforward for the synthesis of anti-cancer drug analogues of benzimidazoquinazolinones.

Recent Trends in Copper-Catalyzed C-H Amination Routes to Biologically Important Nitrogen Scaffolds.

Nitrogen-containing heterocycles have found remarkable applications in natural product research, material sciences, and pharmaceuticals. Although the synthesis of this interesting class of compounds attracted the interest of generations of organic chemists, simple and straightforward assembly methods based on transition-metal catalysis have regularly been elusive. The recent advancements in the development of C-H functionalization have helped in accomplishing the synthesis of a variety of complex heterocycles from simple precursors.

A one-pot copper catalyzed biomimetic route to N-heterocyclic amides from methyl ketones via oxidative C-C bond cleavage.

A direct one-pot Cu-catalyzed biomimetic oxidation of methyl ketones to pharmaceutically important N-heterocyclic amides is reported. The scope of the method is broad, scalable, and mild, and the reaction is tolerant with various acid, base sensitive functionalities with multiple heteroatoms and aryl halides. The extensive mechanistic studies suggest that this reaction follows the Luciferin-Luciferase-like pathway.