Nitrone in l -lyxose series: cycloaddition way for the synthesis of new C-α-fucosides

The dual role of fucosidases: tool or target

Regular intake of fucosylated oligosaccharides has been associated with several benefits for human health, particularly for new-borns. Since these biologically active molecules can be found naturally in human milk, research efforts have been focused on the alternative synthetic routes leading to their production. In particular, utilization of fucosidases to perform stereoselective transglycosylation reactions has been widely investigated. Other reasons that bring these enzymes to the spotlight are their role in viral infections and cancer proliferation. Since their involvement in the pathogenesis of these diseases have been widely described, fucosidases have become a target in newly developed therapies. Finally, activity disorders of biologically important fucosidases can lead to health problems such as fucosidosis. What is common for both mechanisms is the interaction between the enzyme and substrates in and around the active site. Therefore, this review will analyse different substrate structures that have been tested in terms of their interaction with fucosidases active sites, either in synthesis or inhibition reactions. The published results will be compared from this perspective.

Stereoselective synthesis of (2S,3S,4R,5S)-3,4-dihydroxy-2,5-dihydroxymethyl pyrrolidine from L-sorbose

One of the most frequently synthesized iminosugar derivatives is DMDP. Starting from L-sorbose, a practical method for the synthesis of derivatives of this five-membered iminocyclitol has been developed, involving straightforward steps and a convenient selective reduction of a ketoxime intermediate.

Chemo-enzymatic synthesis and glycosidase inhibitory properties of DAB and LAB derivatives

A chemo-enzymatic strategy for the preparation of 2-aminomethyl derivatives of (2R,3R,4R)-2-(hydroxymethyl)pyrrolidine-3,4-diol (also called 1,4-dideoxy-1,4-imino-D-arabinitol, DAB) and its enantiomer LAB is presented. The synthesis is based on the enzymatic preparation of DAB and LAB followed by the chemical modification of their hydroxymethyl functionality to afford diverse 2-aminomethyl derivatives. This strategy leads to novel aromatic, aminoalcohol and 2-oxopiperazine DAB and LAB derivatives. The compounds were preliminarily explored as inhibitors of a panel of commercial glycosidases, rat intestinal disaccharidases and against Mycobacterium tuberculosis, the causative agent of tuberculosis. It was found that the inhibitory profile of the new products differed considerably from the parent DAB and LAB. Furthermore, some of them were active inhibiting the growth of M. tuberculosis.

Iminosugar-ferrocene conjugates as potential anticancer agents

We prepared a series of new iminosugar-ferrocene hybrids displaying potent inhibition of fucosidase (bovine kidney) and inactivation of MDA-MB-231 breast cancer cells proliferation at low micromolar concentrations. The synthetic route brought to light an unprecedented isomerisation of a 2-ethanalylpyrrolidine.

Diastereoselective synthesis of novel iminosugar-containing UDP-Galf mimics: potential inhibitors of UDP-Gal mutase and UDP-Galf transferases

Tetra-O-benzyl-D-glucofuranose was converted into uridine diphosphono-beta-Galf mimics based on an iminosugar skeleton linked to UMP by a 2-hydroxypropyl tether. The synthesis is based on the highly regio- and stereoselective cycloaddition of an original uridin-5'-yl allylphosphonate with a 1,4-dideoxy-1,4-iminogalactitol-derived cyclic nitrone, followed by the reductive elaboration of the cycloaddition product. The resulting iminogalactose-UMP conjugates are novel sugar nucleotide mimics which could be useful as inhibitors of UDP-Gal mutase and UDP-Galf transferases.

Spirocyclopropyl pyrrolidines as a new series of α-l-fucosidase inhibitors

Polyhydroxy 4-azaspiro[2.4]heptane derivatives (spirocyclopropyl iminosugars) were prepared in four to six steps from readily available protected aldoses. The key step of the reaction sequence involves a titanium-mediated aminocyclopropanation of glycononitriles with subsequent cyclization. Five new polyhydroxypyrrolidines so-obtained have been evaluated for their ability to inhibit 16 glycosidases. One of them exhibits selective inhibition of alpha-L-fucosidase from bovine kidney (Ki=1.6 microM, competitive).

Asymmetric synthesis of the l-fuco-nojirimycin, a nanomolar α-l-fucosidase inhibitor

We describe the asymmetric synthesis of the 5-amino-5-deoxy-l-fucose (l-fuco-nojirimycin) which appears as a very potent fucosidase inhibitor with a K(i) value of 1 nM.

Synthesis of Enantiopure Indolizinones by Cascade Ring Enlargements of 4‘-Chlorospiro[cyclopropane-1,5‘-isoxazolidines]

2-Chloro-2-cyclopropylideneacetates (1-Me and 1-Et) and their spiropentane analogues 2 cycloadd enantiopure five-membered cyclic nitrones to give the corresponding adducts (quantitatively, four examples), which undergo cascade ring enlargements to yield indolizinone derivatives (53-70%, four examples). The ring enlargement process is triggered by the abstraction of a bridgehead proton induced by a base and can be suppressed by the presence of a bulky substituent nearby, such as a (triisopropylsilyl)oxy group.

Stereoselective synthesis of (2S,3S,4R,5S)-5-methylpyrrolidine-3,4-diol derivatives that are highly selective α-l-fucosidase inhibitors

N-Phenylaminomethyl benzimidazolyl moieties attached at C-2 of (2S,3S,4R,5S)-5-methylpyrrolidine-3,4-diol increase the potency and selectivity of the inhibitory activity of these systems towards alpha-L-fucosidases.