A solid phase reagent for the capture phosphorylation of carbohydrates and nucleosides.

[figure: see text] A 1% cross-linked divinylbenzene-polystyrene copolymer, containing cyanoethoxy N,N-diisopropylamine phosphine was prepared as a phosphitylating agent. The polymer-bound phosphitylated precursor was subjected to reaction with alcohols in the presence of 1H-tetrazole to produce the corresponding polymer-bound phosphite triesters. These were then oxidized with tert-butyl hydroperoxide to give the polymer-bound monophosphate triesters. Removal of cyanoethoxy on the resin with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) followed by basic cleavage of the p-hydroxybenzyl linker products yielded monophosphate derivatives.

Parallel solution synthesis of a "Carbohybrid" library designed to inhibit galactose-binding proteins.

Parallel solution S-alkylations of a 1-thio-beta-D-galactopyranoside derivative with Michael acceptors and alpha-chloroketones, followed by ketone reductions, reductive aminations, and acylations were developed to yield a library of 1-thio-beta-D-galactopyranosides carrying small and diverse polar-neutral, hydrophobic, aromatic, cationic, or anionic non-carbohydrate aglycon structures. Screening of the library against a panel of galactose recognizing plant lectins revealed microM inhibitors of toxin A of A. precatorius superior to the reference ligands lactose and N-acetyl lactosamine. Such small, monosaccharide based inhibitors are attractive lead-molecules for therapeutic development, since they are low-molecular, hydrolytically stable and more hydrophobic than natural oligosaccharides.

Solid-phase extraction on C18 silica as a purification strategy in the solution synthesis of a 1-thio-beta-D-galactopyranoside library.

A novel strategy for the purification of carbohydrate-based chemical libraries synthesized in solution was developed. Purification of reaction products was accomplished by means of solid-phase extraction enabled by protecting the 2-, 3-, 4-, and 6-hydroxyl groups of a galactose derivative as their hydrophobic O-laurates. The presence of multiple O-laurates allowed adsorption of reaction products onto C18 silica while reagents and by-products were washed away with MeOH. Products were quantitatively eluted with pentane. Purification of products using solid-phase extraction offers the combined advantages of solution synthesis (normal solution reactivity and ease of reaction monitoring) with those of solid-phase synthesis (facile product isolation permitting the use of large excesses of reagents). To demonstrate the utility of the hydrophobic recovery-procedure, tetra-O-lauroyl-beta-D-galactopyranose-1-thiol was subjected to high-yielding reactions with a panel of Michael-acceptors and an alpha-chloro ketone. The resulting ketone adducts were then either reduced to the alcohols or reductively aminated with a selection of amino acids to give 30 different 1-thio-beta-D-galactosides as mixtures of four diastereomers after removal of protecting groups. At each step, the product was separated from the reagents and their by-products by simple adsorption onto C18 silica, washing with MeOH and elution of product with pentane. After completion of the combinatorial chemistry sequence, the O-laurates were cleaved by methanolysis and the product methyl laurate in turn removed from the desired water-soluble products by C18 adsorption. Individual library members were thus conveniently produced on 10-30 mg scales at purity levels of > 90%. One of the 1-thio-beta-D-galactosides thus produced was found to be a competitive inhibitor of the beta-galactosidase from E. coli with Ki value of 1.7 microM.