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.     

Stereoselective synthesis of new rac-quercitols containing hydroxymethyl groups as glucosidase inhibitors

Stereoselective and efficient synthesis of hydroxymethyl-substituted rac-quercitols (13–15) was achieved, starting from cis-furan (Kobayashi, 2008) with photooxygenation reaction, which is readily available by the reduction of cis-phtalic anhydride. α- and β-Glucosidase enzyme activity of the target molecules was evaluated and good inhibitor activity was seen. One- and two-dimensional NMR spectroscopy, IR spectroscopy and X-ray crystallography were utilized in the structure characterization of products.     

Transformation of quercitols into 4-methylenecyclohex-5-ene-1,2,3-triol derivatives, precursors for the chemical chaperones N-octyl-4-epi-β-valienamine (NOEV) and N-octyl-β-valienamine (NOV)

(+)-proto-Quercitol (1) and (-)-vibo-quercitol (2), both of which could be readily prepared by the bioconversion of myo-inositol, were successfully converted into the corresponding 4-methylenecyclohex-5-ene-1,2,3-triol derivatives. These compounds were demonstrated to be suitable precursors, preserving their configurations, for bioactive carba-aminosugars such as the potent chemical chaperone drug candidates, N-octyl-4-epi-β-valienamine (NOEV, 3) and N-octyl-β-valienamine (NOV, 4).     

RCAI-37, 56, 59, 60, 92, 101, and 102, cyclitol and carbasugar analogs of KRN7000: Their synthesis and bioactivity for mouse lymphocytes to produce Th1-biased cytokines

Cyclitol [RCAI-37 (1), 59 (5), 92 (7), and 102 (2)] and carbasugar analogs [RCAI-56 (3), 60 (4), and 101 (6)] of KRN7000 were synthesized through coupling reactions of the corresponding cyclitol or carbasugar derivatives with a cyclic sulfamidate (9) as the key step. Bioassay showed RCAI-56 (3, carbagalactose analog of KRN7000), 59 (5, 1-deoxy-neo-inositol analog), and 92 (7, 1-O-methylated 5) to be remarkably potent stimulants of mouse lymphocytes to produce Th1-biased cytokines, such as interferon-γ, in vivo. RCAI-60 (4, carbafucose analog) and RCAI-101 (6, 6-O-methylated 3) showed strong bioactivity, on the other hands, RCAI-37 (1, myo-inositol analog) and 102 (2, neo-inositol analog) induced little cytokine production.     

Synthesis of 5a,5a′-dicarba-d-glucobioses from conformationally restricted carbaglucosyl triflates using SN2-type inversion with carbaglucosyl nucleophiles

Novel carbohydrate mimics were designed which contain two 5a-carba-d-glucose residues, one each at reducing and nonreducing end, and thus these mimics are 5a,5a′-dicarba-d-glucobioses. Dicarbadisaccharides have attractive features such as stability against endogenous degradative enzymes and being resistant to glycation reactions such as the Maillard reaction. For the synthesis of dicarba-β-d-isomaltose derivatives, the carbaglucosyl triflate locked in ⁴C₁ conformation was synthesized by protecting with butane-2,3-diacetal group or benzylidene group. Then, 5a,5a′-dicarba-β-d-maltose and 5a,5a′-dicarba-α,β-d-trehalose were synthesized by the S_N2-type inversion reaction using 4,6-O-benzylidene carbaglucosyl triflate with 4-OH and 1-OH carba-β-d-glucose derivatives, respectively, and similarly 5a,5a′-dicarba-α-d-isomaltose with 6-OH carba-α-d-glucose derivative.     

Regio- and stereospecific synthesis of rac-carbasugar-based cyclohexane pentols; Investigations of their α- and β-glucosidase inhibitions

In the present study, (3aR,7aS)-1,3,3a,4,7,7a-hexahydroisobenzofuran was submitted to photooxygenation and two isomeric hydroperoxides were successfully obtained. Without any further purification, reduction of the hydroperoxides with titanium tetraisopropoxide catalyzed by dimethyl sulfide gave two alcohol isomers in high yields. After acetylation of alcohol with Ac₂O in pyridine, epoxidation reaction of formed monoacetates with m-CPBA, then chromatographed and followed by hydrolysis of the acetate groups with NH₃ in CH₃OH resulted in the formation of epoxy alcohol isomers respectively. These epoxy alcohol isomers were subjected to trans-dihydroxylation reaction with acid (H₂SO₄) in the presence of water to afford triols. Acetylation of the free hydroxyl groups produced benzofuran triacetates in high yields. Ring-opening reaction of furan triacetates with sulfamic acid catalyzed in the presence of acetic acid/acetic anhydrate and subsequently hydrolysis of the acetate groups with ammonia gave the targeted cyclohexane carbasugar-based pentols. All products were separated and purified by chromatographic and crystallographic methods. Structural analyses of all compounds were conducted by spectral techniques including NMR and X-ray analyses. The biological inhibition activity of the target compounds was tested against glycosidase enzymes, α- and β-glucosidase.