A new access to polyhydroxy piperidines of the azasugar class: synthesis and glycosidase inhibition studies

A new synthetic strategy has been devised to access a variety of polyhydroxylated piperidines belonging to the azasugar class of glycosidase inhibitors. The key precursor (3aR, 7aR)-5-benzyl-2,2-dimethyl-7-methylenehexahydro[1,3]dioxo[4,5-c]pyridine is obtained by photoinduced electron transfer (PET) cyclization of the corresponding alpha-trimethylsilylmethylamine radical cation to the tethered acetylene functionality. The new molecules have been evaluated for inhibitory properties for certain beta-glycosidases and have been found to be moderate to weak inhibitors of the enzymes under study.     

Aziridine carboxylate from D-glucose: synthesis of polyhydroxylated piperidine, pyrrolidine alkaloids and study of their glycosidase inhibition

The D-glucose derived aziridine carboxylate 5 was obtained from (E)-ethyl-6-bromo-1,2-O-isopropylidene-3-O-benzyl-5-deoxy-alpha-D-xylo-5-eno-heptofuranuronate 4 through conjugate addition of benzylamine and in situ intramolecular nucleophilic expulsion of bromine. The regioselective aziridine ring-opening, using water as a nucleophile, resulted in the alpha-hydroxy-beta-aminoester 6, which was exploited in the synthesis of six and five membered azasugars 1b/1c and 2b/2c, respectively. The glycosidase inhibitory activity of the title compounds was evaluated.     

Synthesis and glycosidase inhibition of C-7 modified casuarine derivatives

A series of C-7 modified analogues of casuarine have been synthesized from sugar-derived nitrone and assayed against various glycosidases. Introduction of C-7 aminomethyl or amide group led to sharp decrease of the inhibitory activities.     

Asymmetric synthesis of hydroxy-skipped bishomo-inositols as potential glycosidase inhibitors

Four isomeric hydroxy-skipped bishomo-inositol analogs have been synthesized from both enantiomers of 5-hydroxymethyl-2-cyclohexenone. Sharpless asymmetric dihydroxylation and substrate-directed anionic hydroxymethylation are the key reactions which have been employed successfully for the synthesis of new cyclitols. The synthesized cyclitols have been screened for their inhibitory effect on α- and β-glycosidases.     

Polyhydroxylated homoazepanes and 1-deoxy-homonojirimycin analogues: Synthesis and glycosidase inhibition study

The Johnson-Claisen rearrangement of D-gluco and L-ido-derived allylic orthoesters afforded gamma,delta-unsaturated ester that on ester reduction, epoxidation, regioselective oxirane opening by sodium azide and hydrogenation led to sugar amino alcohols--immediate precursors for 1-deoxy-homonojirimycin 3a,b, and polyhydroxylated homoazepanes 4a,b. Our synthetic approach and glycosidase inhibitory activity is reported.     

Total synthesis of hyacinthacine A1, a glycosidase inhibitor

A practical and enantioselective total synthesis of hyacinthacine A1 is achieved involving syn allylic epoxide opening with retention using Pd catalysis and "domino" hydrogenation (five steps in one pot) sequences.     

Conduramine F-1 epoxides: synthesis and their glycosidase inhibitory activities

Starting from (±)-7-oxanorbornenone ((±)-14), (±)-(1RS,2RS,3SR,6SR)-6-azidocyclohex-4-en-1,2,3-triol ((±)-24) and (±)-(1RS,2RS,3SR,6RS)-6-azidocyclohex-4-en-1,2,3-triol ((±)-26) were obtained. Epoxidation of the latter cyclohexene derivative gave two epoxides (±)-30 and (±)-31 that were converted into (±)-conduramine F-1 epoxides (±)-10 and (±)-11 and N-substituted derivatives (±)-12 and (±)-13. Compound (±)-(1RS,2SR,3RS,4SR,5RS,6SR)-5-({[4-(trifluoromethyl)phenyl]methyl}amino)-7-oxabicyclo[4.1.0]heptane-2,3,4-triol ((±)-12c) is a good, non-competitive inhibitor of β-xylosidase from Aspergillus niger (K_i=2.2 μM), and (±)-(1RS,2RS,3SR,4RS,5SR,6SR)-5-{[(biphenyl-4-yl)methyl]amino}-7-oxabicyclo[4.1.0]heptane-2,3,4-triol ((±)-13d) is a good inhibitor of α-glucosidase from brewer's yeast (K_i=2.8 μM, non-competitive).     

Short synthesis of new salacinol analogues and their evaluation as glycosidase inhibitors

Versatile synthesis of some analogues of the naturally-occurring α-glucosidase inhibitor salacinol (1), involving thioanhydro alditol moieties with erythro, d,l-threo, xylo, ribo, d-arabino and d-manno configurations is described. Nucleophilic attack at the least-hindered carbon atom of an l- or d-protected erythritol cyclic sulfate by the thioanhydro alditol sulfur atom yielded the desired zwitterionic compounds. In addition, the preparation of the cyclic sulfates of 2,4-O-benzylidene-d-erythritol and 2,4-O-isopropylidene-l-erythritol was improved. Enzyme inhibition tests showed that most of the new compounds were weak but specific inhibitors, while good inhibitory activity was found for a six-membered ring analogue (β-glucosidase: K_i=16 μM).     

General approach to glycosidase inhibitors. Enantioselective synthesis of deoxymannojirimycin and swainsonine

[reaction: see text] Deoxymannojirimycin (2) and swainsonine (4) have been synthesized from each enantiomer of the same bicyclic carbamate precursor 7. The key intermediate was prepared by a simple and efficient three-step synthesis involving RCM of the diene 8, which in turn is easily accessible in any configuration from enantiomerically enriched 2,3-epoxy-4-penten-1-ol 9.     

Asymmetric synthesis of 3-amino-4-hydroxy-2-(hydroxymethyl)pyrrolidines as potential glycosidase inhibitors

Three diastereoisomers of 3-amino-4-hydroxy-2-(hydroxymethyl)pyrrolidine have been synthesised by a divergent route starting from trans-4-hydroxy-L-proline. Regio- and stereoselective introduction of the 3-amino and 4-hydroxyl functional groups was achieved using either a tethered aminohydroxylation reaction or by employing intra- and intermolecular epoxide-opening strategies. Preliminary biological data indicate that two of these novel amino pyrrolidines are moderate inhibitors of beta-galactosidase.     

A new class of glycosidase inhibitor: synthesis of salacinol and its stereoisomers

Salacinol (4) is one of the active principles in the aqueous extracts of Salacia reticulata that are traditionally used in Sri Lanka and India for the treatment of diabetes. The syntheses of salacinol (4), the enantiomer of salacinol (5), and a diastereomer (7) are described. The synthetic strategy relies on the selective nucleophilic attack of 2,3,5-tri-O-benzyl-1,4-anhydro-4-thio-D- or L-arabinitol at C-1 of 2,4-O-benzylidene D- or L-erythritol-1,3-cyclic sulfate. The work serves to resolve the ambiguity about the exact structure of salacinol and establishes conclusively the structure of the natural product.     

Synthesis, glycosidase activity and X-ray crystallography of 3-amino-sugars

The cleavage of two sugar epoxides, methyl 2,3-anhydro-alpha-D-mannopyranoside and 2,3-anhydro-alpha-D-allopyranoside, with amines is presented as a method for preparing a library of 3-amino-sugars (methyl 3-amino-3-deoxy-alpha-D-altropyranosides and methyl 3-amino-3-deoxy-alpha-D-glucopyranosides) as potential glycosidase inhibitors. Several of the altropyranosides were micromolar inhibitors of bovine liver beta-galactosidase and almond beta-glucosidase. X-ray crystal structures were determined for one of the methyl 3-amino-3-deoxy-alpha-D-altropyranosides, 4t, and one of the methyl 3-amino-3-deoxy-alpha-D-glucopyranosides, 6d.     

芒柄花素的分离及合成研究

黄芪系豆科黄芪属植物,为最常用中药之一.其中作为药用的有10余种,其中以膜夹黄芪中(Astrgalus membranceus)列为正品.膜夹黄芪中的有效成分之一芒柄花素(Formnonetin)具有抗菌、抗骨质疏松[1]和雌激素样作用[2]、[3]等.     

Isolation and synthesis of isodihydropiperlonguminine

The hexane extract of dried fruits of Piper longum on fractionation afforded a new alkamide, isodihydropiperlonguminine and two phenyl propanoic acid derivatives. The structures of these compounds are established based on spectroscopic evidence and synthesis.     

Novel synthesis of the glycosidase inhibitor deoxymannojirimycin and of a synthetic precursor D-lyxo-hexos-5-ulose

[reaction: see text]. The synthesis of D-lyxo-hexos-5-ulose (5-ketomannose, 1,5-dicarbonyl sugar), a synthetic precursor to the glycoprocessing inhibitor deoxymannojirimycin, was carried out by an in situ epoxidation and hydrolysis of a trimethylsilyl-protected 6-deoxyhex-5-enopyranoside followed by facile removal of the protecting groups. A novel nine-step synthesis of deoxymannojirimycin has also been achieved from methyl alpha-D-mannopyranoside; this involved methanolysis of epoxides derived from an acetylated 1-azido-6-deoxyhex-5-enopyranoside followed by deprotection and catalytic hydrogenation.     

(3S,4R,5R)-3-(2-Hydroxyethyl)piperidine-3,4,5-triol as an isofagomine analogue: synthesis and glycosidase inhibition study

The synthesis of (3S,4R,5R)-3-(2-hydroxyethyl)piperidine-3,4,5-triol 10 has been described from d-glucose. The base promoted cyclization for the construction of the piperdine framework is the key step of the synthesis.     

Stereoselective synthesis of the glycosidase inhibitor australine through a one-pot, double-cyclization strategy

[reaction: see text] A stereocontrolled, convergent synthesis of the alkaloid australine, a glycosidase inhibitor of the pyrrolizidine class, is described. The chiral starting materials were ketone 3, derived from L-erythrulose, and alpha-alkoxy aldehyde 4, prepared from L-malic acid. A key step of the synthesis was the highly stereoselective aldol reaction between 4 and a Z boron enolate derived from 3. Another key step was the one-pot construction of the bicyclic pyrrolizidine system by means of a three-step sequence of SN2 displacements induced by benzylamine on a trimesylate precursor.     

Tuning glycosidase inhibition through aglycone interactions: pharmacological chaperones for Fabry disease and GM1 gangliosidosis

Competitive inhibitors of either α-galactosidase (α-Gal) or β-galactosidase (β-Gal) with high affinity and selectivity have been accessed by exploiting aglycone interactions with conformationally locked sp(2)-iminosugars. Selected compounds were profiled as potent pharmacological chaperones for mutant lysosomal α- and β-Gal associated with Fabry disease and GM(1) gangliosidosis.     

Straightforward chemo-enzymatic synthesis of new aminocyclitols,analogues of valiolamine and their evaluation as glycosidase inhibitors

An efficient fructose-1,6-bisphosphate aldolase mediated synthesis of new aminocyclitol analogues of valiolamine is described. The one-pot process where four stereocentres are created involves the formation of two carbon–carbon bonds. One is catalysed by the aldolase, coupling dihydroxyacetone phosphate to nitrobutyraldehydes. The other is the result of a highly stereoselective intramolecular Henry reaction occurring on the intermediate nitroketones. Depending on the configuration of the hydroxyl which is α to the nitro group, two series of configuration are accessible. The lipase resolution of the nitroalcohol ketal, precursor of the nitroaldehyde, is presented. The inhibition properties of the aminocyclitols obtained after the reduction of the nitro group are evaluated towards five commercial glycosidases.