Sugar-nucleotides such as GDP-mannose, GDP-fucose and UDP-glucose are important biomolecules with a central role in carbohydrate and glycoconjugate biosynthesis, metabolism and cell signalling. Analogues and mimics of naturally occurring sugar-nucleotides are sought after as chemical tools and inhibitor candidates for sugar-nucleotide-dependent enzymes including glycosyltransferases. Many sugar-nucleotides bind to their target glycosyltransferases via coordination of the diphosphate group to a divalent metal cofactor in the active site. The identification of uncharged, chemically stable surrogates for the diphosphate group, with the ability to coordinate to a divalent metal, is therefore an important design criteria for the development of sugar-nucleotide mimics. Here, we describe the rational design and synthesis of a novel class of sugar-nucleotide mimics based on a squaryldiamide scaffold, an uncharged phosphate isostere. We demonstrate by comprehensive NMR titration experiments that the new sugar-nucleotide mimics coordinate efficiently to Mg2+, and provide results from biological studies with a therapeutically relevant mannosyltransferase from Trypanosoma brucei. Our findings suggest that squaryldiamides are a promising template for the development of sugar-nucleotide mimics, and illustrate the considerable potential of the squarylamide group as a fragment for inhibitor design.

Covering: up to 2009

Drug-like molecules with activity against Trypanosoma brucei are urgently required as potential therapeutics for the treatment of African sleeping sickness. Starting from known inhibitors of other glycosyltransferases, we have developed the first small molecular inhibitors of dolicholphosphate mannose synthase (DPMS), a mannosyltransferase critically involved in glycoconjugate biosynthesis in T. brucei. We show that these DPMS inhibitors prevent the biosynthesis of glycosylphosphatidylinositol (GPI) anchors, and possess trypanocidal activity against live trypanosomes.The development of thiazolidinones as dolicholphosphate mannose synthase (DPMS) inhibitors and novel trypanocidal agents (ED50 < 100 μM) is reported.

The direct structural modification of GDP-mannose via the bromination and Suzuki–Miyaura cross-coupling of the unprotected sugar–nucleotide, to produce 8-substituted fluorescent analogues of GDP-mannose.

A convenient and high yielding procedure for the Suzuki–Miyaura cross-coupling of unprotected bromo- and chlorotryptophans in water provides fluorescent aryltryptophans.

A series of novel 5-substituted UDP-glucose derivatives with interesting fluorescent properties and potential applications as sensors for carbohydrate-active enzymes is reported. An efficient synthesis of the target molecules was developed, centred around the Suzuki–Miyaura reaction of (hetero)arylboronic acids with 5-iodo UDP-glucose. Interestingly, the optimised cross-coupling conditions could also be applied successfully to 5-bromo UMP, but not to 5-bromo UDP-glucose.

We report a simple and high-yielding two-step procedure for the preparation of 8-arylated guanosine mono- and triphosphates (8-aryl GXPs). The key step of our synthesis is the Suzuki–Miyaura coupling of unprotected 8-bromo GMP and 8-bromo GTP with various arylboronic acids in aqueous solution. The 8-bromoguanosine 5′-phosphates required as cross-coupling substrates were prepared from 8-bromoguanosine via an optimised Yoshikawa procedure.

The direct structural modification of GDP-mannose via the bromination and Suzuki–Miyaura cross-coupling of the unprotected sugar–nucleotide, to produce 8-substituted fluorescent analogues of GDP-mannose.

A convenient and high yielding procedure for the Suzuki–Miyaura cross-coupling of unprotected bromo- and chlorotryptophans in water provides fluorescent aryltryptophans.

Sugar-nucleotides such as GDP-mannose, GDP-fucose and UDP-glucose are important biomolecules with a central role in carbohydrate and glycoconjugate biosynthesis, metabolism and cell signalling. Analogues and mimics of naturally occurring sugar-nucleotides are sought after as chemical tools and inhibitor candidates for sugar-nucleotide-dependent enzymes including glycosyltransferases. Many sugar-nucleotides bind to their target glycosyltransferases via coordination of the diphosphate group to a divalent metal cofactor in the active site. The identification of uncharged, chemically stable surrogates for the diphosphate group, with the ability to coordinate to a divalent metal, is therefore an important design criteria for the development of sugar-nucleotide mimics. Here, we describe the rational design and synthesis of a novel class of sugar-nucleotide mimics based on a squaryldiamide scaffold, an uncharged phosphate isostere. We demonstrate by comprehensive NMR titration experiments that the new sugar-nucleotide mimics coordinate efficiently to Mg2+, and provide results from biological studies with a therapeutically relevant mannosyltransferase from Trypanosoma brucei. Our findings suggest that squaryldiamides are a promising template for the development of sugar-nucleotide mimics, and illustrate the considerable potential of the squarylamide group as a fragment for inhibitor design.

A series of novel 5-substituted UDP-glucose derivatives with interesting fluorescent properties and potential applications as sensors for carbohydrate-active enzymes is reported. An efficient synthesis of the target molecules was developed, centred around the Suzuki–Miyaura reaction of (hetero)arylboronic acids with 5-iodo UDP-glucose. Interestingly, the optimised cross-coupling conditions could also be applied successfully to 5-bromo UMP, but not to 5-bromo UDP-glucose.