Four-Component Selenoazaindolylation-Alkoxylation of Styrenes for the Synthesis of Azaindolyl β-Alkoxyalkyl Selenoethers.

Due to the medicinal importance of selenoether and azaindole cores, the design and execution of efficient routes to new compounds bearing these groups placed in juxtaposition with each other are important. Again, multicomponent reactions provide fast and efficient access to the compounds of interest. Herein, we present a one-step route to azaindolyl β-alkoxyalkyl selenoethers or azaindolyl β-hydroxyalkyl selenoethers via the one-step reaction of azaindoles, styrenes, a selenium source, and an alcohol or water using a Ce(IV) oxidant.

Step-wise and one-pot syntheses of the trisaccharide repeating unit of Proteus penneri 71 O-antigen.

Due to the importance of the capsular polysaccharides of bacterial pathogens from the perspective of eliciting human immune response and consequential developments of vaccines, they are important targets of synthetic efforts. Herein, we report the chemical synthesis of the trisaccharide repeating unit of the O-antigen capsular polysaccharide of Proteus penneri 71 by step-wise and one-pot approaches using suitably protected monosaccharide building blocks. A comparison of the yields of the products from the two strategies showed that the latter provided a higher yield (67%) than the former (56%).

Chemical synthesis of conjugation-ready tetrasaccharide repeating unit of Escherichia coli O50 O-antigen.

Escherichia coli is a rod-shaped Gram-negative bacterium notorious for provoking diverse human infections. In this study, we report the first total synthesis of tetrasaccharide repeating unit of the cell wall of Gram-negative bacteria Escherichia coli O50 augmented with aminoethyl linker, employing both linear [1+1+1+1] and one-pot [1+1+2] approaches, and later one providing the better yield. As an aminoethyl linker, it can be further utilized for biological purposes; the challenging cis (1 → 4)-β-glycosidic linkage between l-rhamnose and d-glucosamine is addressed here with high stereo control.

Total synthesis of conjugation ready repeating unit of Acinetobacter baumannii strain K141 capsular polysaccharide via a [2 + 2] convergent approach.

Acinetobacter baumannii is a well-known opportunistic gram-negative bacterium responsible for serious concerns to human health due to its high virulence and extensive resistance to numerous antibiotics such as carbapenem, colistin, tigecycline, and many more. Herein, we have conducted the first total synthesis of the repeating unit of Acinetobacter baumannii strain K141 via the convergent [2 + 2] approach featuring the coupling of β-L-Rhap-(1 → 4)-β-D-GlcpNAc and β-D-Galp-(1 → 3)-β-D-GlcpNAc units. The synthesis of the first disaccharide unit involved a stereoselective cis-rhamnosylation that was achieved via the picoloyl-induced hydrogen bond mediated aglycon delivery with high β-stereo control.

Understanding the gelation properties of the fluorophenyl glycosides of arabinoside gelators: experimental and theoretical studies.

In supramolecular gelation, fluorinated gelators are important due to the unique properties displayed by these compounds that arise out of the presence of fluorine atoms. Generally, incorporation of fluorine leads to higher mechanical strength of the gels compared to their non-fluorinated counterparts and this property is enhanced with increasing the number of fluorine atoms. Herein, we show that the incorporation of fluorine into the phenyl ring of phenyl arabinoside allows the molecule to act as a gelator, unlike the non-fluorinated compound.

Chemical synthesis of the O-antigen repeating unit of Actinobacillus actinomycetemcomitans serotype f.

Herein, we report the total synthesis of the trisaccharide repeating unit of the O-antigen of Actinobacillus actinomycetemcomitans serotype f. The trisaccharide comprising of α-(1-2) and α-(1-3)-linked L-rhamnopyranosides backbone with the latter rhamnose containing a branching N-acetyl-d-galactosaminopyranoside at the C2-O via a β-glycosidic bond was synthesized by two methods. Initially, the protected trisaccharide has been synthesized by step-wise assembly of the monosaccharide building blocks and subsequently the former was synthesized by the one-pot assembly of the latter components.

Acetoxy Group-Directed Regioselective C2 Alkenylation of Indoles via Pd-Ag Bimetallic Catalysis.

Regioselective C-H functionalizations of indoles reported to date with directing groups at C3 mainly rely on functional groups that are linked to the indole via C-C bonds. However, groups that are linked to the indole core by C-X linkages are also attractive due to the possibility of further modifications of the C-X bond. Herein, we report a 3-acetoxy directing group for the regioselective C2 alkenylation of indoles via a C-H activation-based, cross-dehydrogenative, oxidative Heck-type reaction.

Visible-light driven acetoxylation and dioxygenation of indoles electron donor-acceptor complexes.

A photoresponsive electron donor-acceptor (EDA) complex, formed by indole and hypervalent iodine such as diacetoxyiodobenzene (DAIB/PIDA, ), was detectable through absorption and emission spectroscopy. Irradiation of the EDA complex with visible light triggered photoinduced single electron transfer (SET) processes that were synthetically useful for the catalyst-free, regioselective acetylation of indoles. The photocatalytic reaction with excess DAIB was also used for the synthesis of isatins.

Stereoselective synthesis of glycosyl azides from anomeric hydroxides via protecting group manipulations.

Herein, we report the direct conversion of anomeric hydroxides to glycosyl azides in one step using diphenylphosphoryl azide. Protecting group manipulations on the hexose sugars have enabled the stereoselective synthesis of either the α-glycosyl azides or the β-anomeric azides in moderate to very good yields. The reaction has also been successfully used to enable the synthesis of β-2-deoxy-2-aminoglucosyl azides.

Organophotoredox-Catalyzed Cross-Dehydrogenative Sulfonamidation of Indoles and Other Heterocycles.

The visible light-triggered regioselective synthesis of 2-sulfonamidoindoles and other 2-sulfonamido heteroarenes is accomplished by the oxidative cross-dehydrogenative coupling of indoles (heteroarenes) with di--toluenesulfonamide or -aryl--toluenesulfonamides. The reaction was catalyzed by eosin-Y through a photoredox route. Detailed mechanistic studies based on control reactions, cyclic voltammetry, and fluorescence quenching have been reported for the elucidation of the mechanistic cycle and revealed that a nitrogen-centered radical is generated, followed by regioselective addition to the heteroarene.

Synthesis of the trisaccharide repeating unit of Stenotrophomonas maltophilia O6 antigen through step-wise and one-pot approaches.

Synthetic conjugate vaccines are an important area of research for the prevention and occurrence of diseases caused by Gram-negative bacteria. For the development of such vaccines, access to the pure and homogeneous oligosaccharide fragments of the bacterial cell surface polysaccharides are necessary. Stenotrophomonas maltophilia is a typical opportunistic Gram-negative bacteria that causes severe pulmonary and other infections; often in hospitalized patients.

Total synthesis of the O-antigen repeating unit of O49 serotype through linear and one-pot assemblies.

Capsular polysaccharides of pathogenic bacteria have been reported to be effective vaccines against diseases caused by them. is a class of enterobacteria of the family Providencia that is responsible for several antibiotic resistant infections, particularly urinary tract infections of patients with prolonged catheterization in hospital settings. Towards the goal of development of vaccine candidates against this pathogen, we herein report the total synthesis of a trisaccharide repeating unit of the O-antigen polysaccharide of the O49 serotype containing the →6)-β-ᴅ-Gal-(1→3)-β-ᴅ-GalNAc(1→4)-α-ᴅ-Gal(1→ linkage.

Short Synthesis of Molnupiravir (EIDD-2801) a Thionated Uridine Intermediate.

Molnupiravir (MK-4482, EIDD-2801) is an experimental drug that has been demonstrated to be effective for the treatment of COVID-19 in human clinical trials. Herein, we report a concise synthesis of the drug a novel thionated derivative that relies on one-pot methodologies, thus decreasing the number of purification steps required. This route provides the drug in an overall 62% yield and >99% purity and uses cheap and readily available bulk chemicals, thereby providing an affordable synthesis of the drug for cheaper and wider global accessibility.

Synthesis of 3-alkenylindoles through regioselective C-H alkenylation of indoles by a ruthenium nanocatalyst.

3-Alkenylindoles are biologically and medicinally very important compounds, and their syntheses have received considerable attention. Herein, we report the synthesis of 3-alkenylindoles via a regioselective alkenylation of indoles, catalysed by a ruthenium nanocatalyst (RuNC). The reaction tolerates several electron-withdrawing and electron-donating groups on the indole moiety.

A gelator-starch blend for dry powder based instant solidification of crude oil at room temperature.

Immobilization of crude oil via solidification is a technique that allows for the control and remediation of oil spills. Gelation using supramolecular gelators is a powerful method for the solidification of crude oil. However, this method suffers from the limitation that the gelator has to be dispersed over the crude oil as a solution in environmentally harmful and volatile carrier solvents.

Partially Acetylated or Benzoylated Arabinose Derivatives as Structurally Simple Organogelators: Effect of the Ester Protecting Group on Gel Properties.

Sugar-based low-molecular-weight gelators (LMWGs) have been used for various applications for a long time. Herein, structurally simple, ester-protected arabinosides are reported as low-molecular-weight organogelators (LMOGs) that are able to gel aromatic solvents, as well as petrol and diesel. Studies on the mechanical strength of the gels, through detailed rheological experiments, indicate that gels from the 1,2-dibenzoylated arabinose gelator possess better mechanical properties than those from the 1,2-diacetylated gelator.

Time Resolved Spectroscopic Studies on a Novel Synthesized Photo-Switchable Organic Dyad and Its Nanocomposite Form in Order to Develop Light Energy Conversion Devices.

UV-vis absorption, steady state and time resolved spectroscopic investigations in pico and nanosecond time domain were made in the different environments on a novel synthesized dyad, 3-(2-methoxynaphthalen-1-yl)-1-(4-methoxyphenyl)prop-2-en-1-one (MNTMA) in its pristine form and when combined with gold (Au) nanoparticles i.e., in its nanocomposite structure.

Enantiomeric organogelators from D-/L-arabinose for phase selective gelation of crude oil and their gel as a photochemical micro-reactor.

Enantiomeric D- or L-arabinose based low molecular-weight organogelators (LMOGs), accessible in a single synthetic step from D-/L-arabinose have been found to be efficient gelators for aromatic solvents and refined and crude oil. The organogel has also been successfully used as a micro-reactor for a photochemical reaction.

PET reactions of cis-dibenzoylalkenes: an efficient trans-reduction of C=C bond.

In contrast to its reaction under catalytic hydrogenation, the first instance of an exclusive and chemoselective trans-reduction of the ene part of derivatives of 5,6-dibenzoylbicyclo[2.2.2]oct-5-en-2-one has been reported under moderate photoinduced electron transfer (PET) conditions using triethylamine (TEA).

Face-selective Diels-Alder reactions between unsymmetrical cyclohexadienes and symmetric trans-dienophile: an experimental and computational investigation.

A combined experimental and theoretical study of the Diels-Alder reactions between 2-trimethylsiloxy-1,3-cyclohexadienes (2-11) and (E)-1,4-diphenylbut-2-ene-1,4-dione (1) is reported. Two diastereomeric products, 5-endo-6-exo- (nx) and 5-exo-6-endo- (xn) dibenzoyl derivatives, are possible with symmetric trans-dienophile (1). While in many cases 5-endo-6-exo product is preferred over the corresponding 5-exo-6-endo product, the product ratio nx:xn is found to vary with the position of substituents on the diene.