Hideya Yuasa

Synthesis of salacinol

Abstract Salacinol, a new type of α-glucosidase inhibitor discovered from the antidiabetic herb, was synthesized for the first time. Under the strategy that salacinol would be synthesized by the coupling reaction between 1,4-epithio- d -arabinitol and the cyclic sulfate of an erythritol derivative, the model coupling reactions between tetrahydrothiophene and versatile cyclic sulfate derivatives were undertaken. These experiments indicated that the 1,3-diol of the cyclic sulfate should be protected with the isopropylidene group, otherwise, even the benzylidene-protected cyclic sulfate decomposed during the reaction. Thus, the salacinol was synthesized using the cyclic sulfate of 1,3- O -isopypropylidene- d -erythritol. The resulting coupling product was deisopropylidenated to afford salacinol. A diastereomer of salacinol was also synthesized.

Synthesis of 5-Thio-L-Fucose and its Inhibitory Effect on Fucosidase

ABSTRACT 5-Thio-L-fucose was synthesized for the first time from D-glucose in 16 steps and -found to have a remarkable inhibitory effect on fucosidases from bovine epididymis (Ki 4.2x10−5 M) and kidney (Ki 8.4 x 10−5 M).

Glycosidase inhibition by cyclic sulfonium compounds.

Inhibitory activities of various cyclic sulfonium compounds including salacinol against several glycosidases were studied and some compounds showed significant inhibition. The sulfonium ion structure was found to be essential for the inhibitory activity. Specific inhibition of salacinol toward rice alpha-glucosidase was ascribed to the tether arm.

SYNTHESIS OF IMINOTHIASUGAR AS A POTENTIAL TRANSITION-STATE ANALOG INHIBITOR OF GLYCOSYLTRANSFER REACTIONS

Iminothiasugar 1, a potential transition-state analog inhibitor of glycosidases, was synthesized in 10 steps from D-xylose.

A tong-like fluorescence sensor for metal ions: perfect conformational switch of hinge sugar by pyrene stacking.

Carbohydrates are among the potential materials for molecular devices, since they are abundant natural resources. However, their rigidity has restricted their use for movable devices. Hinge sugars, 2,4-diamino-2,4-dideoxy-xylopyranosides, shed light on the use of carbohydrates as movable components, as demonstrated by the motion by which all four equatorial substituents can change to an axial orientation in synchronization with a chelation-driven 4C1-1C4 ring flip. In this study, we synthesized a tong-like metal ion sensor, 1,3-di-O-pyrenylmethylated hinge sugar (1), and its model compound, methyl 2,4-di-O-pyrenecarbonyl-xylopyranoside (2), to extend the abilities of hinge sugars as molecular components. From observations of the solvent-dependent conformational and fluorescent behavior of 2, we found that the pyrene stacking assists the 1C4 formation of xylopyranoside by 1.7 kcal mol(-1). We also found that compound 1 produced excimer fluorescence by chelation to Pt2+, Zn2+, Cd2+, Mg2+ or Mn2+, and unexpectedly by addition of acids. 1H NMR measurements ascribed this behavior to the 4C1-1C4 ring flip of hinge sugar in response to chelation or protonation at N2, and revealed rapid and perfect 1C4 formation in the case of Zn2+. These findings will extend the scope of hinge sugars as movable components.

Near-infrared (NIR) up-conversion optogenetics.

Non-invasive remote control technologies designed to manipulate neural functions have been long-awaited for the comprehensive and quantitative understanding of neuronal network in the brain as well as for the therapy of neurological disorders. Recently, it has become possible for the neuronal activity to be optically manipulated using biological photo-reactive molecules such as channelrhodopsin (ChR)-2. However, ChR2 and its relatives are mostly reactive to visible light, which does not effectively penetrate through biological tissues. In contrast, near-infrared (NIR) light (650–1450 nm) penetrates deep into the tissues because biological systems are almost transparent to light within this so-called ‘imaging window’. Here we used lanthanide nanoparticles (LNPs), composed of rare-earth elements, as luminous bodies to activate ChRs since they absorb low-energy NIR light to emit high-energy visible light (up-conversion). Here, we created a new type of optogenetic system which consists of the donor LNPs and the acceptor ChRs. The NIR laser irradiation emitted visible light from LNPs, then induced the photo-reactive responses in the near-by cells that expressed ChRs. However, there remains room for large improvements in the energy efficiency of the LNP-ChR system.

Phylogeny of Galactolipid Synthase Homologs Together with their Enzymatic Analyses Revealed a Possible Origin and Divergence Time for Photosynthetic Membrane Biogenesis

The photosynthetic membranes of cyanobacteria and chloroplasts of higher plants have remarkably similar lipid compositions. In particular, thylakoid membranes of both cyanobacteria and chloroplasts are composed of galactolipids, of which monogalactosyldiacylglycerol (MGDG) is the most abundant, although MGDG biosynthetic pathways are different in these organisms. Comprehensive phylogenetic analysis revealed that MGDG synthase (MGD) homologs of filamentous anoxygenic phototrophs Chloroflexi have a close relationship with MGDs of Viridiplantae (green algae and land plants). Furthermore, analyses for the sugar specificity and anomeric configuration of the sugar head groups revealed that one of the MGD homologs exhibited a true MGDG synthetic activity. We therefore presumed that higher plant MGDs are derived from this ancestral type of MGD genes, and genes involved in membrane biogenesis and photosystems have been already functionally associated at least at the time of Chloroflexi divergence. As MGD gene duplication is an important event during plastid evolution, we also estimated the divergence time of type A and B MGDs. Our analysis indicated that these genes diverged ∼323 million years ago, when Spermatophyta (seed plants) were appearing. Galactolipid synthesis is required to produce photosynthetic membranes; based on MGD gene sequences and activities, we have proposed a novel evolutionary model that has increased our understanding of photosynthesis evolution.

Bisubstrate Analogues as Glycosyltransferase Inhibitors

Oligosaccharides in glycoconjugates such as glycoproteins and glycolipids play important roles in a variety of biological functions. Since glycosyltransferases are responsible for the biosynthesis of these oligosaccharides, inhibitors of glycosyltransferases are targets for drug discovery. Bisubstrate analogues, in which donor and acceptor analogue are covalently attached to each other, offer donors high affinity and acceptors high selectivity. In this review, we describe the design and synthesis of bisubstrate analogues of glycosyltransferases as well as their inhibitory potency hoping to inform the development of potent and selective inhibitors.

Synthesis and Biological Evaluation of α-L-Fucosidase Inhibitors: 5a-Carba-α-L-fucopyranosylamine and Related Compounds

5a-Carba-α-L-fucopyranosylamine (5), an α-glucosidase inhibitor validamine analog possessing an α-L-fucose-type structure, and four related compounds (4 and 6−8) were synthesized and their glycosidase inhibitory potential determined. Carbafucosylamine has already been shown to possess a specific and very strong inhibitory activity against α-L-fucosidase (Ki = 1.2 × 10−8M, bovine kidney). Judging from the activity of the other analogs prepared, this amine might be expected to be a lead compound for development of a new type of α-L-fucosidase inhibitor.

Mannose‐BSA Conjugates: Comparison Between Commercially Available Linkers in Reactivity and Bioactivity

Mannosyl ethanolamine and BSA were conjugated together by their amino groups with various homobifunctional cross‐linker reagents: disuccinimidyl carbonate (DSC), disuccinimidyl glutarate (DSG), disuccinimidyl suberate (DSS), ethylene glycolbis(succinimidylsuccinate) (EGS), 1,5‐difluoro‐2,4‐dinitrobenzene (DFDNB), diethyl squarate (DES), and thiophosgene (TP). The resulting mannose-BSA conjugates were subjected to an enzyme‐linked lectin assay (ELLA)to investigate their affinity to concanvalin A (ConA). With these results, the seven linkers were evaluated on the basis of five criteria, i.e., cost, reactivity, sugar loading, homogeneity, and affinity to ConA. Thus, DSS, DFDNB, and DES seemed to have advantages over the other cross-linking reagents.