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14 pages, 2831 KiB

Open AccessArticle

Cooperatively Catalyzed Activation of Thioglycosides with Iodine and Iron(III) Trifluoromethanesulfonate

by Ashley R. Dent, Aidan M. DeSpain and Alexei V. Demchenko

Molecules 2025, 30(15), 3058; https://doi.org/10.3390/molecules30153058 - 22 Jul 2025

Viewed by 710

Reported herein is a further expansion of the cooperatively catalyzed Koenigs–Knorr glycosylation reaction, known as “the 4K reaction”. It has been discovered that molecular iodine, along with a metal salt and an acid additive, can activate thioglycosides. Previous mechanistic studies showed the interaction [...] Read more.

Reported herein is a further expansion of the cooperatively catalyzed Koenigs–Knorr glycosylation reaction, known as “the 4K reaction”. It has been discovered that molecular iodine, along with a metal salt and an acid additive, can activate thioglycosides. Previous mechanistic studies showed the interaction of the anomeric sulfur with thiophilic iodine; this complex is stable until the halophilic metal salt and the acid additive are added. This new avenue has allowed for the investigation of halophilic promoters that would not activate thioglycosides without iodine. Presented herein is the recent discovery of iron(III) triflate as an efficient activator of thioglycosides via the 4K reaction pathway. Full article

(This article belongs to the Special Issue Contemporary Synthetic Glycoscience: A Theme Issue Dedicated to the Memory of Hans Paulsen)

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10 pages, 4000 KiB

Open AccessArticle

Ferric Chloride Promoted Glycosidation of Alkyl Thioglycosides

by Lacie M. Ridgway, Anupama Das, Melanie L. Shadrick and Alexei V. Demchenko

Molecules 2024, 29(20), 4845; https://doi.org/10.3390/molecules29204845 - 13 Oct 2024

Cited by 1 | Viewed by 1439

Abstract

Reported herein is a new reaction for glycosylation with thioglycosides in the presence of iron(III) chloride. Previously, FeCl₃ was used for the activation of thioglycosides as a Lewis acid co-promoter paired with NIS. In the reported process, although 5.0 equiv of FeCl [...] Read more.

Reported herein is a new reaction for glycosylation with thioglycosides in the presence of iron(III) chloride. Previously, FeCl₃ was used for the activation of thioglycosides as a Lewis acid co-promoter paired with NIS. In the reported process, although 5.0 equiv of FeCl₃ are needed to activate thioglycosides most efficiently, no additives were used, and the reactions with reactive glycosyl donors smoothly proceeded to completion in 1 h at 0 °C. This work showcases a new direction in developing glycosylation methods using greener and earth-abundant activators. Full article

(This article belongs to the Special Issue Special Issue in Honor of Prof. David Crich’s 65th Birthday for His Outstanding Contributions to Carbohydrate Chemistry)

21 pages, 2193 KiB

Open AccessFeature PaperReview

Applications of Nanoporous Gold in Therapy, Drug Delivery, and Diagnostics

by Palak Sondhi, Dhanbir Lingden, Jay K. Bhattarai, Alexei V. Demchenko and Keith J. Stine

Metals 2023, 13(1), 78; https://doi.org/10.3390/met13010078 - 28 Dec 2022

Cited by 16 | Viewed by 3850

Abstract

Nanoporous gold (np-Au) has promising applications in therapeutic delivery. The promises arise from its high surface area-to-volume ratio, ease of tuning shape and size, ability to be modified by organic molecules including drugs, and biocompatibility. Furthermore, np-Au nanostructures can generate the photothermal effect. [...] Read more.

Nanoporous gold (np-Au) has promising applications in therapeutic delivery. The promises arise from its high surface area-to-volume ratio, ease of tuning shape and size, ability to be modified by organic molecules including drugs, and biocompatibility. Furthermore, np-Au nanostructures can generate the photothermal effect. This effect can be used either for controlled release of drugs of therapeutic importance or for destroying cancer cells by heating locally. Despite the enormous potential, the research on the therapeutical use of the np-Au is still in its early stage. In this review, we discuss the current progress and future directions of np-Au for therapeutic applications. Full article

(This article belongs to the Special Issue Advances in Nanoporous Metallic Materials)

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13 pages, 5837 KiB

Open AccessArticle

Activation of Thioglycosides with Copper(II) Bromide

by Faranak Pooladian, Samira Escopy and Alexei V. Demchenko

Molecules 2022, 27(21), 7354; https://doi.org/10.3390/molecules27217354 - 29 Oct 2022

Cited by 7 | Viewed by 2952

Abstract

Reported herein is a new protocol for glycosidation of alkyl and aryl thioglycosides in the presence of copper(II) bromide. While the activation with CuBr₂ alone was proven suitable for reactive glycosyl donors, the activation of less reactive donors was more efficient in [...] Read more.

Reported herein is a new protocol for glycosidation of alkyl and aryl thioglycosides in the presence of copper(II) bromide. While the activation with CuBr₂ alone was proven suitable for reactive glycosyl donors, the activation of less reactive donors was more efficient in the presence of triflic acid as an additive. A variety of thioglycoside donors in reactions with different glycosyl acceptors were investigated to determine the initial scope of this reaction. Full article

(This article belongs to the Special Issue Carbohydrate Chemistry II)

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20 pages, 8885 KiB

Open AccessFeature PaperArticle

Nanoporous Gold Monolith for High Loading of Unmodified Doxorubicin and Sustained Co-Release of Doxorubicin-Rapamycin

by Jay K. Bhattarai, Dharmendra Neupane, Bishal Nepal, Alexei V. Demchenko and Keith J. Stine

Nanomaterials 2021, 11(1), 208; https://doi.org/10.3390/nano11010208 - 15 Jan 2021

Cited by 9 | Viewed by 3787

Abstract

Nanoparticles (NPs) have been widely explored for delivering doxorubicin (DOX), an anticancer drug, to minimize cardiotoxicity. However, their efficiency is marred by a necessity to chemically modify DOX, NPs, or both and low deposition of the administered NPs on tumors. Therefore, alternative strategies [...] Read more.

Nanoparticles (NPs) have been widely explored for delivering doxorubicin (DOX), an anticancer drug, to minimize cardiotoxicity. However, their efficiency is marred by a necessity to chemically modify DOX, NPs, or both and low deposition of the administered NPs on tumors. Therefore, alternative strategies should be developed to improve therapeutic efficacy and decrease toxicity. Here we report the possibility of employing a monolithic nanoporous gold (np-Au) rod as an implant for delivering DOX. The np-Au has very high DOX encapsulation efficiency (>98%) with maximum loading of 93.4 mg cm⁻³ without any chemical modification required of DOX or np-Au. We provide a plausible mechanism for the high loading of DOX in np-Au. The DOX sustained release for 26 days from np-Au in different pH conditions at 37 °C, which was monitored using UV-Vis spectroscopy. Additionally, we encased the DOX-loaded np-Au with rapamycin (RAPA)-trapped poly(D,L-lactide-co-glycolide) (PLGA) to fabricate an np-Au@PLGA/RAPA implant and optimized the combinatorial release of DOX and RAPA. Further exploiting the effect of the protein corona around np-Au and np-Au@PLGA/RAPA showed zero-order release kinetics of DOX. This work proves that the np-Au-based implant has the potential to be used as a DOX carrier of potential use in cancer treatment. Full article

(This article belongs to the Special Issue Gold Nanoparticles as Host Nanosystems)

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14 pages, 15166 KiB

Open AccessArticle

FEM Simulation of THz Detector Based on Sb and Bi₈₈Sb₁₂ Thermoelectric Thin Films

by Anastasiia S. Tukmakova, Alexei V. Asach, Anna V. Novotelnova, Ivan L. Tkhorzhevskiy, Natallya S. Kablukova, Petr S. Demchenko, Anton D. Zaitsev and Mikhail K. Khodzitsky

Appl. Sci. 2020, 10(6), 1929; https://doi.org/10.3390/app10061929 - 11 Mar 2020

Cited by 5 | Viewed by 3545

Abstract

A terahertz (THz) detector based on thermoelectric thin films was simulated using the finite elements method. The thermoelectric circuit consisted of

S b

and

B i_{88} S b_{12}

150-nm films on the mica substrate.

S b

, [...] Read more.

A terahertz (THz) detector based on thermoelectric thin films was simulated using the finite elements method. The thermoelectric circuit consisted of

S b

and

B i_{88} S b_{12}

150-nm films on the mica substrate.

S b

,

B i_{88} S b_{12}

, and mica-substrate properties have been measured experimentally in the THz frequency range. The model of electromagnetic heating was used in order to estimate possible heating of

S b

-

B i_{88} S b_{12}

contact. THz radiation power varied from 1

μ

W to 50 mW, and frequency varied in the range from 0.3 to 0.5 THz. The calculations showed a temperature difference of up to 1 K, voltage up to 0.1 mV, and responsivity of several mVW

^{- 1}

. The results show that thin

S b

and

B i - S b

thermoelectric films can be used for THz radiation detection at room temperatures. Full article

(This article belongs to the Special Issue Terahertz Sensing)

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11 pages, 1433 KiB

Open AccessArticle

Hydrolysis of Glycosyl Thioimidates by Glycoside Hydrolase Requires Remote Activation for Efficient Activity

by Laure Guillotin, Zeinab Assaf, Salvatore G. Pistorio, Pierre Lafite, Alexei V. Demchenko and Richard Daniellou

Catalysts 2019, 9(10), 826; https://doi.org/10.3390/catal9100826 - 1 Oct 2019

Cited by 5 | Viewed by 3969

Abstract

Chemoenzymatic synthesis of glycosides relies on efficient glycosyl donor substrates able to react rapidly and efficiently, yet with increased stability towards chemical or enzymatic hydrolysis. In this context, glycosyl thioimidates have previously been used as efficient donors, in the case of hydrolysis or [...] Read more.

Chemoenzymatic synthesis of glycosides relies on efficient glycosyl donor substrates able to react rapidly and efficiently, yet with increased stability towards chemical or enzymatic hydrolysis. In this context, glycosyl thioimidates have previously been used as efficient donors, in the case of hydrolysis or thioglycoligation. In both cases, the release of the thioimidoyl aglycone was remotely activated through a protonation driven by a carboxylic residue in the active site of the corresponding enzymes. A recombinant glucosidase (DtGly) from Dictyoglomus themophilum, previously used in biocatalysis, was also able to use such glycosyl thioimidates as substrates. Yet, enzymatic kinetic values analysis, coupled to mutagenesis and in silico modelling of DtGly/substrate complexes demonstrated that the release of the thioimidoyl moiety during catalysis is only driven by its leaving group ability, without the activation of a remote protonation. In the search of efficient glycosyl donors, glycosyl thioimidates are attractive and efficient. Their utility, however, is limited to enzymes able to promote leaving group release by remote activation. Full article

(This article belongs to the Special Issue Novel Enzyme and Whole-Cell Biocatalysts)

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29 pages, 4734 KiB

Open AccessFeature PaperReview

Preparation, Modification, Characterization, and Biosensing Application of Nanoporous Gold Using Electrochemical Techniques

by Jay K. Bhattarai, Dharmendra Neupane, Bishal Nepal, Vasilii Mikhaylov, Alexei V. Demchenko and Keith J. Stine

Nanomaterials 2018, 8(3), 171; https://doi.org/10.3390/nano8030171 - 16 Mar 2018

Cited by 72 | Viewed by 9441

Abstract

Nanoporous gold (np-Au), because of its high surface area-to-volume ratio, excellent conductivity, chemical inertness, physical stability, biocompatibility, easily tunable pores, and plasmonic properties, has attracted much interested in the field of nanotechnology. It has promising applications in the fields of catalysis, bio/chemical sensing, [...] Read more.

Nanoporous gold (np-Au), because of its high surface area-to-volume ratio, excellent conductivity, chemical inertness, physical stability, biocompatibility, easily tunable pores, and plasmonic properties, has attracted much interested in the field of nanotechnology. It has promising applications in the fields of catalysis, bio/chemical sensing, drug delivery, biomolecules separation and purification, fuel cell development, surface-chemistry-driven actuation, and supercapacitor design. Many chemical and electrochemical procedures are known for the preparation of np-Au. Recently, researchers are focusing on easier and controlled ways to tune the pores and ligaments size of np-Au for its use in different applications. Electrochemical methods have good control over fine-tuning pore and ligament sizes. The np-Au electrodes that are prepared using electrochemical techniques are robust and are easier to handle for their use in electrochemical biosensing. Here, we review different electrochemical strategies for the preparation, post-modification, and characterization of np-Au along with the synergistic use of both electrochemistry and np-Au for applications in biosensing. Full article

(This article belongs to the Special Issue Nanoporous Gold and Other Related Materials)

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