Site-Selective Photobromination of O-Acetylated Carbohydrates in Benzotrifluoride

Ferrier photobromination enables direct synthetic access to valuable 5-C-bromosugars but has limitations that restrict its broader use. The reaction is typically conducted in CCl4 heated at reflux with irradiation by broad spectrum, energy-inefficient heat lamps. Herein, we demonstrate that the reaction proceeds rapidly and efficiently with PhCF3 as a safe and environmentally benign alternative to CCl4 at mild temperatures (≤40 °C) inside a compact photoreactor fitted with purple light-emitting diodes (LEDs).

Therapeutic Role of Pharmacological Chaperones in Lysosomal Storage Disorders: A Review of the Evidence and Informed Approach to Reclassification

The treatment landscape for lysosomal storage disorders (LSDs) is rapidly evolving. An increase in the number of preclinical and clinical studies in the last decade has demonstrated that pharmacological chaperones are a feasible alternative to enzyme replacement therapy (ERT) for individuals with LSDs. A systematic search was performed to retrieve and critically assess the evidence from preclinical and clinical applications of pharmacological chaperones in the treatment of LSDs and to elucidate the mechanisms by which they could be effective in clinical practice. Publications were screened according to the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) reporting guidelines. Fifty-two articles evaluating 12 small molecules for the treatment of seven LSDs are included in this review. Overall, a substantial amount of preclinical and clinical data support the potential of pharmacological chaperones as treatments for Fabry disease, Gaucher disease, and Pompe disease. Most of the available clinical evidence evaluated migalastat for the treatment of Fabry disease. There was a lack of consistency in the terminology used to describe pharmacological chaperones in the literature. Therefore, the new small molecule chaperone (SMC) classification system is proposed to inform a standardized approach for new, emerging small molecule therapies in LSDs.

New ε-N-thioglutaryl-lysine derivatives as SIRT5 inhibitors: Chemical synthesis, kinetic and crystallographic studies

SIRT5 has been implicated in various physiological processes and human diseases, including cancer. Development of new highly potent, selective SIRT5 inhibitors is still needed to investigate disease-related mechanisms and therapeutic potentials. We here report new ε-N-thioglutaryllysine derivatives, which were designed according to SIRT5-catalysed deacylation reactions. These ε-N-thioglutaryllysine derivatives displayed potent SIRT5 inhibition, of which the potential photo-crosslinking derivative 8 manifested most potent inhibition with an IC₅₀ value of 120 nM to SIRT5, and low inhibition to SIRT1-3 and SIRT6. The enzyme kinetic assays revealed that the ε-N-thioglutaryllysine derivatives inhibit SIRT5 by lysine-substrate competitive manner. Co-crystallographic analyses demonstrated that 8 binds to occupy the lysine-substate binding site by making hydrogen-bonding and electrostatic interactions with SIRT5-specific residues, and is likely positioned to react with NAD⁺ and form stable thio-intermediates. Compound 8 was observed to have low photo-crosslinking probability to SIRT5, possibly due to inappropriate position of the diazirine group as observed in SIRT5:8 crystal structure. This study provides useful information for developing drug-like inhibitors and cross-linking chemical probes for SIRT5-related studies.

Synthesis of Uronic Acid 1-Azasugars as Putative Inhibitors of α-Iduronidase, β-Glucuronidase and Heparanase

1-Azasugar analogues of l-iduronic acid (l-IdoA) and d-glucuronic acid (d-GlcA) and their corresponding enantiomers have been synthesized as potential pharmacological chaperones for mucopolysaccharidosis I (MPS I), a lysosomal storage disease caused by mutations in the gene encoding α-iduronidase (IDUA). The compounds were efficiently synthesized in nine or ten steps from d- or l-arabinose, and the structures were confirmed by X-ray crystallographic analysis of key intermediates. All compounds were inactive against IDUA, although l-IdoA-configured 8 moderately inhibited β-glucuronidase (β-GLU). The d-GlcA-configured 9 was a potent inhibitor of β-GLU and a moderate inhibitor of the endo-β-glucuronidase heparanase. Co-crystallization of 9 with heparanase revealed that the endocyclic nitrogen of 9 forms close interactions with both the catalytic acid and catalytic nucleophile.

Discovery of small-molecule protein stabilizers toward exogenous alpha-l-iduronidase to reduce the accumulated heparan sulfate in mucopolysaccharidosis type I cells

Synthesis of a series of l-iduronic acid (IdoA)- and imino-IdoA-typed C-glycosides for modulating α-l-iduronidase (IDUA) activity is described. In an enzyme inhibition study, IdoA-typed C-glycosides were more potent than imino-IdoA analogs, with the most potent IdoA-typed C-glycoside 27c showing an IC₅₀ value of 1 μM. On the other hand, co-treatment of 12 with rh-α-IDUA in mucopolysaccharidosis type I (MPS I) fibroblasts exhibited a nearly 3-fold increase of the IDUA activity, resulting in a clear reduction of the accumulated heparan sulfate (HS) compared to the exogenous enzyme treatment alone. This is the first report of small molecules facilitating IDUA stabilization, enhancing enzyme activity, and reducing accumulated HS in MPS I cell-based assays, which reveals that small molecules as rh-α-IDUA stabilizers to improve enzyme replacement therapy (ERT) efficacy toward MPS I is feasible and promising.

Harnessing polyhydroxylated pyrrolidines as a stabilizer of acid alpha-glucosidase (GAA) to enhance the efficacy of enzyme replacement therapy in Pompe disease

To discover small molecules as acid alpha-glucosidase (GAA) stabilizers for potential benefits of the exogenous enzyme treatment toward Pompe disease cells, we started from the initial screening of the unique chemical space, consisting of sixteen stereoisomers of 2-aminomethyl polyhydroxylated pyrrolidines (ADMDPs) to find out two primary stabilizers 17 and 18. Further external or internal structural modifications of 17 and 18 were performed to increase structural diversity, followed by the protein thermal shift study to evaluate the GAA stabilizing ability. Fortunately, pyrrolidine 21, possessing an l-arabino-typed configuration pattern, was identified as a specific potent rh-GAA stabilizer, enabling the suppression of rh-GAA protein denaturation. In a cell-based Pompe model, co-administration of 21 with rh-GAA protein significantly improved enzymatic activity (up to 5-fold) compared to administration of enzyme alone. Potentially, pyrrolidine 21 enables the direct increase of ERT (enzyme replacement therapy) efficacy in cellulo and in vivo.

Synthesis of Nitrone-derived Pyrrolidine Scaffolds and Their Combinatorial Libraries to Develop Selective α-l-Rhamnosidase Inhibitors

A general and flexible approach toward the development of α-l-rhamnosidase (α-l-Rha-ase) inhibitors is described. Five enantiopure poly-substituted pyrrolidine-based scaffolds bearing the C1-aminomethyl moiety were designed and synthesized from five-membered cyclic nitrones. Each structurally diversified amide library of these scaffolds was rapidly generated via combinatorial parallel synthesis and applied for in-situ inhibition study against α-l-Rha-ase, allowing us to efficiently identify new inhibition hits. Surprisingly, all promising inhibitors are derived from the same scaffold 3. Among them, the most potent and selective inhibitor is pyrrolidine 19 with Ki =0.24 μM, approximately 24-fold more potent than the reference compound DAA (Ki =5.7 μM). It is the first study to comprehensively prepare pyrrolidine-based scaffolds and libraries for inhibition study against α-l-Rha-ase.

Resveratrol-Based MTDLs to Stimulate Defensive and Regenerative Pathways and Block Early Events in Neurodegenerative Cascades

By replacing a phenolic ring of (E)-resveratrol with an 1,3,4-oxadiazol-2(3H)-one heterocycle, new resveratrol-based multitarget-directed ligands (MTDLs) were obtained. They were evaluated in several assays related to oxidative stress and inflammation (monoamine oxidases, nuclear erythroid 2-related factor, quinone reductase-2, and oxygen radical trapping) and then in experiments of increasing complexity (neurogenic properties and neuroprotection vs okadaic acid). 5-[(E)-2-(4-Methoxyphenyl)ethenyl]-3-(prop-2-yn-1-yl)-1,3,4-oxadiazol-2(3H)-one (4e) showed a well-balanced MTDL profile: cellular activation of the NRF2-ARE pathway (CD = 9.83 μM), selective inhibition of both hMAO-B and QR2 (IC₅₀s = 8.05 and 0.57 μM), and the best ability to promote hippocampal neurogenesis. It showed a good drug-like profile (positive in vitro central nervous system permeability, good physiological solubility, no glutathione conjugation, and lack of PAINS or Lipinski alerts) and exerted neuroprotective and antioxidant actions in both acute and chronic Alzheimer models using hippocampal tissues. Thus, 4e is an interesting MTDL that could stimulate defensive and regenerative pathways and block early events in neurodegenerative cascades.

Synthesis of L-hexoses: an Update

Over the years, carbohydrates have increasingly become an important class of compounds contributing significantly to the target specific drug discovery and vaccine development. Several oligosaccharides contain L-hexoses that are biologically relevant as therapeutic and diagnostic tools. Since, L-hexoses and deoxy L-hexoses are not readily available in large amount and pure form, attention is drawn towards development of cost effective and high yielding synthetic routes for their procurement. In this review we give an update on the recent developments in strategies for synthesis of L-hexoses and deoxy L-hexoses.

Rapid Synthesis of a Natural Product-Inspired Uridine Containing Library

The preparation of natural product-inspired nucleoside analogs using solution-phase parallel synthesis is described. The key intermediates containing alkyne and N-protected amino moieties were developed to allow for further skeleton and substituent diversity using click chemistry and urea or amide bond formation. Rapid purification was accomplished using solid-phase extraction. The obtained library comprised 80 molecules incorporating two diversity positions and one chiral center, each of which was efficiently prepared in good purity and acceptable overall yield. A bacterial morphology study was also performed.