Synthesis of five-membered cyclic ethers by reaction of 1,4-diols with dimethyl carbonate

LNP-RNA-engineered adipose stem cells for accelerated diabetic wound healing

Adipose stem cells (ASCs) have attracted considerable attention as potential therapeutic agents due to their ability to promote tissue regeneration. However, their limited tissue repair capability has posed a challenge in achieving optimal therapeutic outcomes. Herein, we conceive a series of lipid nanoparticles to reprogram ASCs with durable protein secretion capacity for enhanced tissue engineering and regeneration. In vitro studies identify that the isomannide-derived lipid nanoparticles (DIM1T LNP) efficiently deliver RNAs to ASCs. Co-delivery of self-amplifying RNA (saRNA) and E3 mRNA complex (the combination of saRNA and E3 mRNA is named SEC) using DIM1T LNP modulates host immune responses against saRNAs and facilitates the durable production of proteins of interest in ASCs. The DIM1T LNP-SEC engineered ASCs (DS-ASCs) prolong expression of hepatocyte growth factor (HGF) and C-X-C motif chemokine ligand 12 (CXCL12), which show superior wound healing efficacy over their wild-type and DIM1T LNP-mRNA counterparts in the diabetic cutaneous wound model. Overall, this work suggests LNPs as an effective platform to engineer ASCs with enhanced protein generation ability, expediting the development of ASCs-based cell therapies.

Close the cancer-immunity cycle by integrating lipid nanoparticle-mRNA formulations and dendritic cell therapy

Effective cancer immunotherapy is usually blocked by immunosuppressive factors in the tumour microenvironment, resulting in tumour promotion, metastasis and recurrence. Here we combine lipid nanoparticle-mRNA formulations and dendritic cell therapy (named CATCH) to boost the cancer-immunity cycle via progressive steps to overcome the immunosuppressive tumour microenvironment. Multiple types of sugar-alcohol-derived lipid nanoparticles are conceived to modulate the cancer-immunity cycle. First, one type of lipid nanoparticle containing CD40 ligand mRNA induces robust immunogenic cell death in tumoural tissues, leading to the release of tumour-associated antigens and the expression of CD40 ligand. Next, dendritic cells engineered by another type of lipid nanoparticle encapsulating CD40 mRNA are adoptively transferred, which are then activated by the CD40 ligand molecules in tumoural tissues. This promotes the secretion of multiple cytokines and chemokines, and the upregulation of co-stimulatory molecules on dendritic cells, which are crucial for reprogramming the tumour microenvironment and priming the T-cell responses. After dendritic cells present tumour-associated antigens to T cells, all the above stepwise events contribute to boosting a potent tumour-specific T-cell immunity that eradicates established tumours, suppresses distal lesions and prevents tumour rechallenge.

Solvent-Driven Selectivity on the One-Step Catalytic Synthesis of Manoyl Oxide Based on a Novel and Sustainable “Zeolite Catalyst–Solvent” System

Application of a novel “zeolite catalyst–solvent” system for the sustainable one-step synthesis of the terpenoid manoyl oxide, the potential precursor of forskolin and ambrox. Manoyl oxide high-yield and large-scale production over a zeolite catalyst has been infeasible so far, while this system results in 90% yields at 135 °C and atmospheric pressure. Substrate-controlled methodology is used to achieve selectivity. Solvent-driven catalysis is shown, as the activation energy barrier decreases in the presence of appropriate solvents, being 62.7 and 93.46 kJmol−1 for a glyme-type solvent and dodecane, respectively. Finally, catalyst acidity is key parameter for the process.

Graphic Abstract

Biomass-derived chemical substitutes for bisphenol A: recent advancements in catalytic synthesis

Bisphenol A is an oil-derived, large market volume chemical with a wide spectrum of applications in plastics, adhesives and thermal papers. However, bisphenol A is not considered safe due to its endocrine disrupting properties and reproductive toxicity. Several functional substitutes of bisphenol A have been proposed in the literature, produced from plant biomass. Unless otherwise specified, the present review covers the most significant contributions that appeared in the time span January 2015-August 2019, describing the sustainable catalytic synthesis of rigid diols from biomass derivatives. The focus is thereupon on heterogeneous catalysis, use of green solvents and mild conditions, cascade processes in one-pot, and continuous flow setups. More than 500 up-to-date references describe the various substitutes proposed and the catalytic methods for their manufacture, broken down according to the main biomass types from which they originate.

Dehydrative Formation of Isosorbide from Sorbitol over Poly(ionic liquid)-Covalent Organic Framework Hybrids

In this study, the covalent bonding of linear poly(ionic liquid)s (PILs) with covalent organic frameworks (COFs) was accessed by copolymerization of a vinyl-decorated COF with 4-vinylbenzyl chloride, followed by quaternization with tertiary amines. The resultant PIL-COF composite by anchoring a proper content of vinyl sites on the COF-based comonomer retains the crystallinity and porosity, thereby facilitating access of the reactants to the catalytic active sites. As a proof of concept, the dehydrative transformation of sorbitol into isosorbide was selected as a benchmark reaction, whose rate improved significantly in the presence of PIL-COF-0.33 compared with those of individual components and the mesoporous PIL counterpart due to uniform pore sizes and flexible linear catalytic chains. In addition, the hybrids bearing a chemical cross-linkage between PILs and COFs are robust, and PIL-COF-0.33 can be recovered and reused for 10 runs without significant reactivity loss. These findings provide the basis for a novel design concept for achieving both efficient and stable IL catalysis.

Dialkyl Carbonates in the Green Synthesis of Heterocycles

This review focuses on the use of dialkyl carbonates (DACs) as green reagents and solvents for the synthesis of several 5- and 6-membered heterocycles including: tetrahydrofuran and furan systems, pyrrolidines, indolines, isoindolines, 1,4-dioxanes, piperidines, and cyclic carbamates. Depending on the heterocycle investigated, the synthetic approach used was different. Tetrahydrofuran systems, pyrrolidines, indolines, isoindoline, and 1,4-dioxanes were synthesized using dimethyl carbonate (DMC) as sacrificial molecule (BAc2/BAl2 mechanism). Cyclic carbamates, namely 1,3-oxazin-2-ones, were prepared employing DACs as carbonylating agents, either by BAc2/BAl2 mechanism or through a double BAc2 mechanism. Piperidines were synthetized taking advantage of the anchimeric effect of a new family of dialkyl carbonates, i.e., mustard carbonates. Finally, in the case 5-hydroxymethylfurfural (HMF), DMC has been employed as efficient extracting solvent of this extensively investigated bio-based platform chemical from the reaction mixture. These synthetic approaches demonstrate, once again, the great versatility of DACs and their-yet to be fully explored-potential as green reagents and solvents in the synthesis of heterocycles.

Nonclassical Mechanism in the Cyclodehydration of Diols Catalyzed by a Bifunctional Iridium Complex

1,4- and 1,5-diols undergo cyclodehydration upon treatment with cationic N-heterocyclic carbene (NHC)-IrIII complexes to give tetrahydrofurans and tetrahydropyrans, respectively. The mechanism was investigated, and a metal-hydride-driven pathway was proposed for all substrates, except for very electron-rich ones. This contrasts with the well-established classical pathways that involve nucleophilic substitution.

Recent Advances in Phthalan and Coumaran Chemistry

Oxygen-containing heterocycles are common in biologically active compounds. In particular, phthalan and coumaran cores are found in pharmaceuticals, organic electronics, and other useful medical and technological applications. Recent research has expanded the methods available for their synthesis. This Minireview presents recent advances in the chemistry of phthalans and coumarans, with the goal of overcoming synthetic challenges and facilitating the applications of phthalans and coumarans.

Synthesis of cyclic ethers by cyclodehydration of 1,n-diols using heteropoly acids as catalysts

Heteropoly acids were used as catalysts for cyclodehydration of various 1,n-diols. Cyclodehydration of butane-1,4-diol, pentane-1,5-diol and hexane-1,6-diol catalysed by H3PW12O40 gave tetrahydrofuran, tetrahydropyran and oxepane, respectively. Cyclodehydration of diethylene glycol, triethylene glycol, diethylene glycol monomethyl ether and polyethylene glycol 200 catalysed by H3PW12O40 gave 1,4-dioxane. In particular, cyclodehydration of hexane-1,6-diol gave an excellent yield of oxepane (80%). The selectivity exhibited by the H3PW12O40 catalyst was even better than that exhibited by other reported catalyst systems for similar cyclodehydration reactions.

5-Membered cyclic ethers via phenonium ion mediated cyclization through carbonate chemistry

Cyclization of 2-(2-hydroxyethyl)phenol via DMC chemistry in acidic conditions is herein discussed for the first time. Reaction conditions have been investigated and optimized. This substrate is quite appealing as it incorporates a 2-hydroxyethyl moiety in ortho to the aromatic hydroxyl group capable of stabilizing the related phenonium ion. When the reaction mechanism was investigated via theoretical calculations, the results suggest that the most favorable pathway encompasses a DMC-mediated formation of the phenonium ion that is converted into the 2-(2-methoxyethyl)phenol. The related cyclic ether is then formed via intramolecular cyclization of this intermediate. This peculiar cyclization reaction is another example of the versatility of DMC herein used as solvent, methoxycarbonylation agent and leaving group in the intramolecular cyclization leading to the phenonium ion.

β-Aminocarbonates in Regioselective and Ring Expansion Reactions

The reactivity of β-aminocarbonates as anisotropic electrophiles has been investigated with several phenols. Products distribution shows that the regioselectivity of the anchimerically driven alkylation reaction depends on the nucleophiles. The results suggest that in the presence of nucleophiles that are also good leaving groups, the reaction takes place under thermodynamic control favoring the attack on the most sterically hindered carbon of the cyclic aziridinium intermediate. Furthermore, when an enantiomerically pure pyrrolidine-based carbonate was used, the reaction with phenols proceeds via a bicyclic aziridinium intermediate leading to the stereoselective synthesis of optically active 3-substituted piperidines via ring expansion reaction. These results were confirmed both by NMR spectroscopy and X-ray diffraction analysis.

Synergistic Configuration of Diols as Brønsted Bases

As viscous hydroxylic organic compounds, diols are of interest for their functional molecular conformation, which is based on inter- and intramolecular hydrogen (H)-bonds. By utilising steady-state electronic and vibrational spectroscopy, time-resolved fluorescence spectroscopy, and computational analyses, we report the association of the hydroxyl groups of diols via intra- or intermolecular H-bonds to enhance their reactivity as a base. Whereas the formation of an intermolecularly H-bonded dimer is requisite for diols of weak intramolecular H-bond to extract a proton from a model strong photoacid, a well-configured single diol molecule with an optimised intramolecular H-bond is revealed to serve as an effective Brønsted base with increased basicity. This observation highlights the collective role of H-bonding in acid-base reactions, and provides mechanistic backgrounds to understand the reactivity of polyols in the acid-catalysed dehydration for the synthesis of cyclic ethers at the molecular level.

One-Pot Preparation of Dimethyl Isosorbide from d-Sorbitol via Dimethyl Carbonate Chemistry

Direct synthesis of dimethyl isosorbide (DMI) from d-sorbitol via dimethyl carbonate (DMC) chemistry is herein first reported. High yield of DMI was achieved using the nitrogen superbase 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) as catalyst and performing the reaction in a stainless steel autoclave by increasing the temperature from 90 to 200 °C. In this procedure, DMC features its full capacity acting in the different steps of the process as carboxymethylating, leaving-group (cyclization), and methylating agent; DMC is also employed as the reaction media.

Cyclic ether synthesis from diols using trimethyl phosphate

Cyclic ethers are simply synthesized from diols by using trimethyl phosphate at room temperature.

DFT and experimental analysis of aluminium chloride as a Lewis acid proton carrier catalyst for dimethyl carbonate carboxymethylation of alcohols

In silico and physical experimental data led to a potential acid (AlCl3) catalysed mechanism for DMC carboxymethylation.

Isosorbide and dimethyl carbonate: a green match

In this review the reactivity of the bio-based platform compounds D-sorbitol and isosorbide with green reagents and solvent dimethyl carbonate (DMC) is reported. Dehydration of D-sorbitol via DMC in the presence of catalytic amounts of base is an efficient and viable process for the preparation of the industrially relevant anhydro sugar isosorbide. This procedure is "chlorine-free", one-pot, environmental friendly and high yielding. The reactivity of isosorbide with DMC is equally interesting as it can lead to the formation of dicarboxymethyl isosorbide, a potential monomer for isosorbide-based polycarbonate, and dimethyl isosorbide, a high boiling green solvent. The peculiar reactivity of isosorbide and the non-toxic properties of DMC represent indeed a green match leading to several industrial appealing potential applications.

The neighbouring effect of isosorbide and its epimers in their reactions with dimethyl carbonate

Abstract The reactions of isosorbide and its epimers, isomannide and isoidide, with dimethyl carbonate have been herein investigated as easy access to bio-based products by a free-halogen chemistry approach. Isosorbide and its epimers show a different reactivity in bimolecular nucleophilic substitution with dimethyl carbonate (DMC). Carboxymethylation reaction was carried out in the presence of DMC and a weak base resulting in the high-yielding synthesis of dicarboxymethyl derivatives. Isomannide was the most reactive anhydro sugar due to the less sterically hindered exo position of the OH groups. On the other hand, methylation of isosorbide and its epimers, conducted in the presence of a strong base and DMC, showed the higher reactivity of the endo hydroxyl group, isoidide being the most reactive epimer. This result has been ascribed to the neighboring effect due to the combination of the oxygen in β-position and the intramolecular hydrogen bond within the anhydro sugar structure. Methylation reactions were also conducted in autoclave at high temperature with the amphoteric catalyst hydrotalcite using DMC as reagent and solvent. In this case, the reactivity of the epimers resulted quite differently with isosorbide being the most reactive reagent possibly as a result of the structure of hydrotalcite comprising of both acidic and basic sites. The neighboring effect was observed with good evidence in these methylation reactions.

1,3-Oxazinan-2-ones via carbonate chemistry: a facile, high yielding synthetic approach

A high yielding synthesis of 1,3-oxazinan-2-ones starting from 3-amino-1-propanols and ethylene carbonate (EC) in the presence of catalytic amount of triazabicyclodecene (TBD) is herein reported. The formation of six-membered cyclic carbonates was achieved by intermolecular cyclization reaction via double BAc2 mechanism. Cyclization reactions have been carried out in neat as EC acted both as solvent and reagent. Pure 1,3-oxazinan-2-ones were isolated in high yield by simple liquid-liquid extraction. Further purification can be achieved by recrystallization. The reaction resulted of general application on different substrates including an aryl bis(3-amino-proan-1-ol) compound.

Mustard carbonate analogues

Sulfur and nitrogen (half-)mustard carbonate analogues are a new class of compounds, easily synthesized by methoxycarbonylation reaction of the parent alcohols with dialkyl carbonates. In this work, their reactivity as novel, green electrophiles is reported. Reactions have been conducted in autoclave conditions at high temperature (180°C), under pressure and in absence of any base, as well as, in neat at atmospheric pressure, lower temperature (150°C) and in the presence of a catalytic amount of a base. Several nucleophiles have been investigated resulting, in some cases, in unexpected compounds, i.e., six-membered heterocycle piperidine. Reaction mechanism and kinetics have been studied confirming that these compounds retain the anchimeric effect of their mustard gas analogues, without being toxic. Noteworthy, a symmetrical nitrogen mustard carbonate has also been employed as reagent in the preparation of a new family of macrocycles i.e., azacrowns, before not easily accessible.

Exploring the interactions between isoprenoid chain and labdenediol diphosphate synthase based on molecular docking and quartz crystal microbalance

Many natural products and biosynthetic intermediates contain isoprenoid chains. Isoprenoid chains are believed to interact with some proteins in the biological systems, but such interactions remain poorly understood. Here labdenediol diphosphate synthase (LPPS) was used as a model to explore the molecular interactions involving isoprenoid chains. Both homology modeling and docking simulation results indicated that binding form between isoprenoid chain and LPPS is dominated by hydrophobic forces in one binding site. The interactions were also examined via quartz crystal microbalance (QCM) technology using synthetic isoprenoid chain-contained probes. The binding constant (1.51 μM(-1)), binding site number (n = 1) and key amino acid residues (Y196, F262, W266, F301, F308, W398, W439, and Y445) were obtained. Both computational and QCM results suggested that LPPS interacts strongly with farnesyl and geranylgeranyl groups. These interactions are primarily caused by hydrophobic and π-π interaction nature. Together, this study provided insightful information to understand molecular interactions between isoprenoid chains and proteins.

The neighbouring effect of isosorbide and its epimers in their reactions with dimethyl carbonate

ABSTRACT – The reactions of isosorbide and its epimers, isomannide and isoidide, with dimethyl carbonate have been herein investigated as easy access to bio-based products by a free-halogen chemistry approach. Isosorbide and its epimers show a different reactivity in bimolecular nucleophilic substitution with DMC. Carboxymethylation reaction was carried out in the presence of DMC and a weak base resulting in the high-yielding synthesis of dicarboxymethyl derivatives. Isomannide was the most reactive anydro sugars due to the less sterically hindered exo position of the OH groups. On the other hand, methylation of isosorbide and its epimers, conducted in the presence of a strong base and DMC, showed the higher reactivity of the endo hydroxyl group, isoidide being the most reactive epimer. This result has been ascribed to the neighbouring effect due to the combination of the oxygen in β-position and the intramolecular hydrogen bond within the anhydro sugar structure. Methylation reactions were also conducted in autoclave at high temperature with the amphoteric catalyst hydrotalcite using DMC as reagent and solvent. In this case, the reactivity of the epimers resulted quite different with isosorbide being the most reactive reagent possibly as a result of the structure of hydrotalcite comprising of both acidic and basic sites. The neighbouring effect was observed with good evidence in these methylation reactions.

Behaviour of iprit carbonate analogues in solventless reactions

Sulfur iprit carbonate analogues showed to undergo nucleophilic substitution with several substrates in neat conditions at atmospheric pressure, in the presence and in the absence of a catalytic amount of base.

Carbonate phosphonium salts as catalysts for the transesterification of dialkyl carbonates with diols. The competition between cyclic carbonates and linear dicarbonate products

Methylcarbonate and bicarbonate methyltrioctylphosphonium salts were excellent catalysts for the transesterification of dialkyl carbonates with diols: cyclic or linear carbonates are obtained.