A potent bicyclic inhibitor of a family 27 α-galactosidase

New α-galactosidase-inhibiting aminohydroxycyclopentanes

A set of cyclopentanoid α-galactosidase ligands was prepared from a partially protected ω-eno-aldose via a reliable (2 + 3)-cycloaddition protocol with slightly modified conditions. The obtained N-benzylisoxazolidine ring was selectively opened and the configuration of the hydroxymethylgroup was inverted. Consecutive deprotection provided an aminocyclopentane, which was N-alkylated to furnish a set of potential α-galactosidase inhibitors. Their glycosidase inhibitory activities were screened with a panel of standard glycosidases of biological significance.

A concise and robust synthesis of new cyclopentanoid competitive inhibitors of α-galactosidases related to Fabry's disease and other α-galactosidase related disorders.

Revealing the mechanism for covalent inhibition of glycoside hydrolases by carbasugars at an atomic level

Mechanism-based glycoside hydrolase inhibitors are carbohydrate analogs that mimic the natural substrate’s structure. Their covalent bond formation with the glycoside hydrolase makes these compounds excellent tools for chemical biology and potential drug candidates. Here we report the synthesis of cyclohexene-based α-galactopyranoside mimics and the kinetic and structural characterization of their inhibitory activity toward an α-galactosidase from Thermotoga maritima (TmGalA). By solving the structures of several enzyme-bound species during mechanism-based covalent inhibition of TmGalA, we show that the Michaelis complexes for intact inhibitor and product have half-chair (²H₃) conformations for the cyclohexene fragment, while the covalently linked intermediate adopts a flattened half-chair (²H₃) conformation. Hybrid QM/MM calculations confirm the structural and electronic properties of the enzyme-bound species and provide insight into key interactions in the enzyme-active site. These insights should stimulate the design of mechanism-based glycoside hydrolase inhibitors with tailored chemical properties.

Mechanism-based inhibitors of glycoside hydrolases are useful probes for basic research and represent potential drug candidates. Here, the authors present a series of mechanism-based covalent α-galactosidase inhibitors and elucidate the kinetic and structural basis of their inhibitory activity.

Carba-cyclophellitols Are Neutral Retaining-Glucosidase Inhibitors

The conformational analysis of glycosidases affords a route to their specific inhibition through transition-state mimicry. Inspired by the rapid reaction rates of cyclophellitol and cyclophellitol aziridine-both covalent retaining β-glucosidase inhibitors-we postulated that the corresponding carba "cyclopropyl" analogue would be a potent retaining β-glucosidase inhibitor for those enzymes reacting through the 4H3 transition-state conformation. Ab initio metadynamics simulations of the conformational free energy landscape for the cyclopropyl inhibitors show a strong bias for the 4H3 conformation, and carba-cyclophellitol, with an N-(4-azidobutyl)carboxamide moiety, proved to be a potent inhibitor (Ki = 8.2 nM) of the Thermotoga maritima TmGH1 β-glucosidase. 3-D structural analysis and comparison with unreacted epoxides show that this compound indeed binds in the 4H3 conformation, suggesting that conformational strain induced through a cyclopropyl unit may add to the armory of tight-binding inhibitor designs.

Biosynthesis and Biological Activity of Carbasugars

The first synthesis of carbasugars, compounds in which the ring oxygen of a monosaccharide had been replaced by a methylene moiety, was described in 1966 by Professor G. E. McCasland’s group. Seven years later, the first true natural carbasugar (5a-carba-R-D-galactopyranose) was isolated from a fermentation broth of Streptomyces sp. MA-4145. In the following decades, the chemistry and biology of carbasugars have been extensively studied. Most of these compounds show interesting biological properties, especially enzymatic inhibitory activities, and, in consequence, an important number of analogues have also been prepared in the search for improved biological activities. The aim of this review is to give coverage on the progress made in two important aspects of these compounds: the elucidation of their biosynthesis and the consideration of their biological properties, including the extensively studied carbapyranoses as well as the much less studied carbafuranoses.

Synthesis and evaluation of influenza A viral neuraminidase candidate inhibitors based on a bicyclo[3.1.0]hexane scaffold

We describe the synthesis of constrained oseltamivir analogues designed to mimic the proposed boat conformation of the enzymatic transition state.

Design and synthesis of galactose-6-OH-modified α-galactosyl ceramide analogues with Th2-biased immune responses

In this study, a simple type of O-6 analogue of KRN7000 was synthesized starting from galactosyl iodide and d-lyxose.

Short synthesis of a benzyl ether-protected building block for the synthesis of carbocyclic galactopyranose mimics

A versatile intermediate for the synthesis of galactose-mimicking carbasugars was synthesised from tetrabenzyl galactose in five steps and 30% overall yield. The reaction sequence uses an L-proline-mediated aldol reaction as key step. The reaction sequence was run on several grams of material.

Mechanistic insights into glycosidase chemistry

The enzymatic hydrolysis of the glycosidic bond continues to gain importance, reflecting the critically important roles complex glycans play in health and disease as well as the rekindled interest in enzymatic biomass conversion. Recent advances include the broadening of our understanding of enzyme reaction coordinates, through both computational and structural studies, improved understanding of enzyme inhibition through transition state mimicry and fascinating insights into mechanism yielded by physical organic chemistry approaches.

Lessons from nature: biomimetic organocatalytic carbon-carbon bond formations

Nature utilizes simple C2 and C3 building blocks, such as dihydroxyacetone phosphate (DHAP), phosphoenolpyruvate (PEP), and the "active aldehyde" in various enzyme-catalyzed carbon-carbon bond formations to efficiently build up complex organic molecules. In this Perspective, we describe the transition from using enantiopure chemical synthetic equivalents of these building blocks, employing our SAMP/RAMP hydrazone methodology and metalated chiral alpha-amino nitriles, to the asymmetric organocatalytic versions developed in our laboratory. Following this biomimetic strategy, the DHAP equivalent 2,2-dimethyl-1,3-dioxan-5-one (dioxanone) has been used in the proline-catalyzed synthesis of carbohydrates, aminosugars, carbasugars, polyoxamic acid, and various sphingosines. Proline-catalyzed aldol reactions involving a PEP-like equivalent have also allowed for the asymmetric synthesis of ulosonic acid precursors. By mimicking the "active aldehyde" nucleophilic acylations in Nature catalyzed by the thiamine-dependent enzyme, transketolase, enantioselective N-heterocyclic carbene-catalyzed benzoin and Stetter reactions have been developed. Finally, based on Nature's use of domino reactions to convert simple building blocks into complex and highly functionalized molecules, we report on our development of biomimetic asymmetric multicomponent domino reactions which couple enamine and iminium catalysis.