Synthesis and glycosidase inhibitory activity of aminocyclitols with a C6- or a C7-ring

Stereoselective syntheses of 3-aminocyclooctanetriols and halocyclooctanetriols

The efficient synthesis of two new stereoisomeric 3-aminocyclooctanetriols and their new halocyclitol derivatives starting from cis,cis-1,3-cyclooctadiene are reported. Reduction of cyclooctene endoperoxide, obtained by photooxygenation of cis,cis-1,3-cyclooctadiene, with zinc yielded a cyclooctene diol followed by acetylation of the hydroxy group, which gave dioldiacetate by OsO₄/NMO oxidation. The cyclooctane dioldiacetate prepared was converted to the corresponding cyclic sulfate via the formation of a cyclic sulfite in the presence of catalytic RuO₄. The reaction of this cyclic sulfate with a nucleophilic azide followed by the reduction of the azide group provided the target, 3-aminocyclooctanetriol. The second key compound, bromotriol, was prepared by epoxidation of the cyclooctenediol with m-chloroperbenzoic acid followed by hydrolysis with HBr(g) in methanol. Treatment of bromotriol with NaN₃ and the reduction of the azide group yielded the other desired 3-aminocyclooctanetriol. Hydrolysis of the epoxides with HCl(g) in methanol gave stereospecifically new chlorocyclooctanetriols.

Synthesis of novel seven-membered carbasugars and evaluation of their glycosidase inhibition potentials

Here, we report the synthesis of five novel seven-membered carbasugar analogs. We adopted a chiral-pool strategy starting from the cheap and readily available d-mannitol to synthesize these ring-expanded carbasugars. Apart from several regioselective protecting group manipulations, these syntheses involved Wittig olefination and ring-closing metathesis as the key steps. We observed an unprecedented deoxygenation reaction of an allylic benzyl ether upon treatment with H₂/Pd during the synthesis. Preliminary biological evaluation of the carbasugars revealed that these ring expanded carbasugars act as inhibitors of various glycosidases. This study highlights the importance of the synthesis of novel ring expanded carbasugars and their biological exploration.

Here, we report the synthesis of five novel seven-membered carbasugar analogs.

An efficient synthesis of chloro-aminocyclooctanediol and aminocyclooctanetriol: an unexpected acetolysis product

A concise and efficient synthesis of 2-amino-4-chlorocyclooctanediol, aminocyclooctanetriols and unusual 1,3-hydride shift during the ring opening reaction of epoxide is described.

Quercitol: From a Taxonomic Marker of the Genus Quercus to a Versatile Chiral Building Block of Antidiabetic Agents

Quercitol is a cyclohexanepentol that has been recognized as a biomarker of plants in genus Quercus, which includes oak. As a result of its glucose-like structure, it has been introduced as an alternative chiral building block in the synthesis of several bioactive compounds. Our continuing investigations on the synthesis of antidiabetic agents from quercitol have demonstrated that this chiral synthon can generate diverse structural features with improved hypoglycemic activity.

Total syntheses of five uvacalols: structural validation of uvacalol A, uvacalol B and uvacalol C and disproval of the structures of uvacalol E and uvacalol G

Uvacalols are novel carbasugars belonging to the family of C7-cyclitols, and are isolated from the roots of the medicinal plant, Uvaria calamistrata. In this study, we report the first syntheses of five uvacalols starting from a cheap and easily available chiral pool starting material, D-mannitol, in their optically pure form. D-Mannitol was converted to the alkene 2 through a series of regioselective and chemoselective transformations by following our previously reported strategies. Alkene 2 was converted to the enal 5 through a series of protective group manipulations. Enal 5 was converted to the diene 6 by the addition of vinyl magnesium bromide. Ring closing metathesis of the diene 6 using Grubbs’ second generation catalyst installed the core cyclohexenyl unit. Through several iterative and selective manipulations of various hydroxyl groups, uvacalol A, uvacalol B, uvacalol C, uvacalol E and uvacalol G were synthesized. A comparison of the (1)H NMR and (13)C NMR data of these synthesized molecules with the reported data, revealed that the reported structures of uvacalols A–C are correct and those of uvacalols E and G are wrong.

Synthesis and evaluation of galacto-noeurostegine and its 2-deoxy analogue as glycosidase inhibitors

An epimer of the known glycosidase inhibitor noeurostegine, galacto-noeurostegine, was synthesised in 21 steps from levoglucosan and found to be a potent, competitive and highly selective galactosidase inhibitor of Aspergillus oryzae β-galactosidase.

Total syntheses and structural validation of lincitol A, lincitol B, uvacalol I, uvacalol J, and uvacalol K

First total syntheses of lincitol A, lincitol B, uvacalol I, uvacalol J and uvacalol K were achieved in racemic form, validating their structure from a common intermediate, which was synthesized in six steps from low-cost and extensively available myo-inositol.

Enantioselective synthesis of cocaine C-1 analogues using sulfinimines (N-sulfinyl imines)

The first examples of cocaine analogues having substituents (methyl, ethyl, n-propyl, n-pentyl, and phenyl) at the C-1 position of the cocaine tropane skeleton were prepared by heating sulfinimine-derived α,β-unsaturated pyrrolidine nitrones. In the presence of the Lewis acid Al(O(t)Bu)(3) the nitrones undergo an intramolecular [3 + 2] cycloaddition to give tricyclic isoxazolidines that were transformed in three steps to the cocaine analogues. In the absence of the Lewis acid, lactams were formed resulting from rearrangement of the nitrone to an oxaziridine. A novel Pd- and base-promoted rearrangement of methanesulfonate salts of isoxazolidine to bridge bicyclic[4.2.1]isoxazolidines was discovered.

A linchpin carbacyclization approach for the synthesis of carbanucleosides

A convenient synthesis of carbanucleosides, with both enantiomers equally accessible, is reported. The key step is a tandem linchpin cyclization process to give access to substituted carbafuranose derivatives having the correct relative stereochemistry for subsequent nucleobase introduction with inversion of configuration at C1. This was illustrated by the synthesis of 2',3'-dideoxycarbathymidine via a convergent nucleobase introduction and of 2',3'-dideoxy-6'-hydroxycarbauridine via a linear nucleobase introduction. Both methods relied on Mitsunobu chemistry, and the first example of the Mukaiyama modification of the Mitsunobu reaction involving nucleobases as nucleophiles is reported.

Synthesis and glycosidase inhibitory activity of new hexa-substituted C8-glycomimetics

Background

Glycosidases are involved in several metabolic pathways and the development of inhibitors is an important challenge towards the treatment of diseases, such as diabetes, cancer and viral infections including AIDS. Thus, inhibition of intestinal α-glucosidases can be used to treat diabetes through the lowering of blood glucose levels, and α-glucosidase inhibitors are being marketed against type 2 (non-insulinodependent mellitus) diabetes (i.e.: Glyset^® or Diastabol^®, Basen^® and Glucor^® or Precose^®).

Results

In that context, new C8-carbasugars and related aminocyclitols have been targeted in order to study the effect of the enhanced flexibility and of the new spatial distribution displayed by these structures on their adaptability in the active site of the enzymes. The synthesis of these new C8-glycomimetics is described from enantiomerically pure C₂-symmetrical polyhydroxylated cyclooctenes. Their obtention notably involved a syn-dihydroxylation, and more extended functionalization through formation of a cis-cyclic sulfate followed by amination and subsequent reductive amination. This strategy involving the nucleophilic opening of a cis-cyclic sulfate by sodium azide is to our knowledge the first example in C8-series. It revealead to be an efficient alternative to the nucleoplilic opening of an epoxide moiety which proved unsuccessful in this particular case, due to the hindered conformation of such epoxides as demonstrated by X-ray cristallographic analysis.

Conclusion

The biological activity of the synthesized glycomimetics has been evaluated towards 24 commercially available glycosidases. The weak observed activities can probably be related to the spatial disposition of the hydroxy and amino groups which depart too much from that realized in glycomimetics such as valiolamine, voglibose and valienamine. Nevertheless, the synthetic strategy described here is efficient and general, and could be extended to increase the diversity of the glycosidase inhibitors obtained since this diversity is introduced in an ultimate step of the synthesis.

New aminocyclitols as modulators of glucosylceramide metabolism

A series of 13 aminocyclitol derivatives belonging to two different families is described. Their configuration is governed by the regio- and stereocontrolled epoxide opening of a suitably protected conduritol-B epoxide. Studies on several glycosyl processing enzymes indicate that some of them are good inhibitors of glucosylceramide hydrolase. A rationale to account for preliminary structure-activity relationships is provided.

Synthesis of polyhydroxylated piperidines and evaluation as glycosidase inhibitors

A series of 16 new chiral nonracemic polyhydroxylated piperidines was synthesized utilizing several chiral beta-amino-alcohols. They act as a nitrogen source, chirality inducer and iminium stabilizer, in the desymmetrization of meso-trihydroxylated glutaraldehyde. The biological activity of these compounds towards several glycosidases (alpha-D-glucosidase, alpha-D-mannosidase, alpha-L-fucosidase) has been evaluated.

Determination of the structures of four new isomeric cyclitols

A series of impurities, which were all of the same molecular formula, C17H33NO7, were obtained in the process of voglibose synthesis. After isolation and purification, four isomeric cyclitols were completely assigned by 2D NMR experiments. One of the compounds was established by single-crystal X-ray diffraction analysis as 5,6-dideoxy-5-{[2-hydroxy-1-(hydroxymethyl)ethyl]amino}-1-C-(methoxycyclohexylmethyl)-D-epi-inositol.