Jong Chan Son

Inhibition of HIV replication by amino-sugar derivatives

The plant alkaloids castanospermine, dihydroxymethyldihydroxypyrrolidine and deoxynojirimycin have recently been shown to have potential anti‐HIV activity [(1987) Proc. Natl. Acad. Sci. USA 84, 8120–8124; (1987) Nature 330, 74–77; (1987) Lancet i, 1025–1026]. They are thought to act by inhibiting α‐glucosidase I, an enzyme involved in the processing of N‐linked oligosaccharides on glycoproteins. We report here the relative efficacy of a spectrum of amino‐sugar derivatives as inhibition of HIV cytopathicity. Several α‐glucosidase inhibitors and α‐fucosidase inhibitors were found to be active at concentrations which were non‐cytotoxic.

Polyhydroxylated pyrrolidines from sugar lactomes: Synthesis of 1,4-dideoxy-1,4-imino-d-glucitol from d-galactonolactone and syntheses of 1,4-dideoxy-1,4-imino-d-allitol, 1,4-dideoxy-1,4-imino-d-ribitol, and (2s,3r,4s)-3,4-dihydroxyproline from d-gulonolactone

Abstract The use of readily available sugar lactones in the synthesis of polyhydroxylated pyrrolidines is illustrated by the preparation of the glucosidase inhibitor 1,4-dideoxy-1, 4-imino-D-glucitol from D-galactonolactone and by the conversion of D-gulonolactone into 1,4-dideoxy-l,4-imino-D-allitol, 1,4-dideoxy-l,4-imino-D-ribitol, and (2S,3R,4S)-3,4-dihydroxyproline.

Glucose analogue inhibitors of glycogen phosphorylase: from crystallographic analysis to drug prediction using GRID force-field and GOLPE variable selection.

Several inhibitors of the large regulatory enzyme glycogen phosphorylase (GP) have been studied in crystallographic and kinetic experiments. GP catalyses the first step in the phosphorylysis of glycogen to glucose-l-phosphate, which is utilized via glycolysis to provide energy to sustain muscle contraction and in the liver is converted to glucose. alpha-D-Glucose is a weak inhibitor of glycogen phosphorylase form b (GPb, K(i) = 1.7 mM) and acts as a physiological regulator of hepatic glycogen metabolism. Glucose binds to phosphorylase at the catalytic site and results in a conformational change that stabilizes the inactive T state of the enzyme, promoting the action of protein phosphatase 1 and stimulating glycogen synthase. It has been suggested that in the liver, glucose analogues with greater affinity for glycogen phosphorylase may result in a more effective regulatory agent. Several N-acetyl glucopyranosylamine derivatives have been synthesized and tested in a series of crystallographic and kinetic binding studies with GPb. The structural results of the bound enzyme-ligand complexes have been analysed together with the resulting affinities in an effort to understand and exploit the molecular interactions that might give rise to a better inhibitor. Comparison of the N-methylacetyl glucopyranosylamine (N-methylamide, K(i) = 0.032 mM) with the analogous beta-methylamide derivative (C-methylamide, K(i) = 0.16 mM) illustrate the importance of forming good hydrogen bonds and obtaining complementarity of van der Waals interactions. These studies also have shown that the binding modes can be unpredictable but may be rationalized with the benefit of structural data and that a buried and mixed polar/non-polar catalytic site poses problems for the systematic addition of functional groups. Together with previous studies of glucose analogue inhibitors of GPb, this work forms the basis of a training set suitable for three-dimensional quantitative structure-activity relationship studies. The molecules in the training set are void of problems and potential errors arising from the alignment and bound conformations of each of the ligands since the coordinates were those determined experimentally from the X-ray crystallographic refined ligand-enzyme complexes. The computational procedure described in this work involves the use of the program GRID to describe the molecular structures and the progam GOLPE to obtain the partial least squares regression model with the highest prediction ability. The GRID/GOLPE procedure performed using 51 glucose analogue inhibitors of GPb has good overall predictivity [standard deviation of error predictions (SDEP) = 0.98 and Q(2) = 0.76] and has shown good agreement with the crystallographic and kinetic results by reliably selecting regions that are known to affect the binding affinity.

Synthesis from D-mannose of 1,4-dideoxy-1,4-imino-L-ribitol and of the α-mannosidase inhibitor 1,4-dideoxy-1,4-imino-D-talitol

Abstract The syntheses of 1,4-dideoxy-l,4-imino-L-ribitol and of 1,4-dideoxy-l,4-imino-D-talitol from D-mannose are described. 1,4-Dideoxy-l,4-imino-D-talitol is a specific and competitive inhibitor of human liver α-mannosidase in vitro and also blocks the lysosomal catabolism of asparigine-linked glycans of glycoproteins in vivo .

Anomeric spirohydantoins of mannofuranose : approaches to novel anomeric amino acids by an oxidative ring contraction

Bromine-induced oxidative ring contraction of an α-amino-δ-lactone gave a mixture of α-aminotetrahydrofurancarboxylic esters which may allow the preparation of stable amino acid derivatives at the anomeric position of mannofuranose. The synthesis of N-phenylhydantoins at the anomeric position of mannofuranose is reported.

Spirohydantoins of glucofuranose: Analogues of hydantocidin

Abstract Routes from both γ- and δ-glucoheptonolactones to spirohydantoins of glucofuranose are described, affording further analogues of hydantocidin. It may be that the glucofuranose isomers are more stable than the glucopyranose forms.

Chiral oxetanes from sugar lactones: Synthesis of derivatives of 3,5-anhydro-1,2-O-isopropyl-α-D-glucuronic acid and of 3,5-anhydro-1,2-O-isopropyllidene-β-L-iduronic acid

Abstract Ring contraction reactions of triflates of α-hydroxy-γ-lactones provide an approach to the synthesis of chiral polyfunctionalised oxetanes from sugars. Treatment of 1,2-0-isopropylidene-5-0-trifluoromethanesulphonyl-α-D-glucuronolactone with benzylamine or with potassium carbonate in methanol gave ring contraction reactions to form oxetanes in good yield.

The ring contraction of δ-lactones with leaving group α-substituents: a strategy for the synthesis of 2,5-disubstituted highly functionalised homochiral tetrahydrofurans

Treatment of derivatives of δ-lactones having a leaving group at C-2 with methanol in the presence of base gives methyl tetrahydrofuran-α-carboxylates in good to excellent yield with a high degree of stereocontrol of the carbon substituents at C-2 and C-5.

The design of potential antidiabetic drugs: experimental investigation of a number of β-D-glucose analogue inhibitors of glycogen phosphorylase

Summaryα-D-glucose is a weak inhibitor (Ki=1.7 mM) of glycogen phosphorylase (GP) and acts as physiological regulator of hepatic glycogen metabolism; it binds to GP at the catalytic site and stabilizes the inactive T state of the enzyme promoting the action of protein phosphatase 1 and stimulating glycogen synthase. The three-dimensional structures of T state rabbit muscle GPb and the GPb-α-D-glucose complex have been exploited in the design of better regulators of GP that could shift the balance between glycogen synthesis and glycogen degradation in favour of the former. Close examination of the catalytic site with α-D-glucose bound shows that there is an empty pocket adjacent to the β-1-C position. β-D-glucose is a poorer inhibitor (Ki=7.4 mM) than α-D-glucose, but mutarotaion has prevented the binding of β-D-glucose in T state GP crystals. A series of β-D-glucose analogues has been designed and tested in kinetic and crystallographic experiments. Several compounds have been discovered that have an increased affinity for GP than the parent compound.

Acid-catalysed transformation of α-trifluoromethanesulfonates of γ- and δ-lactones into 2,5-disubstituted homochiral tetrahydrofurans

Excellent yields of methyl tetrahydrofuran-α-carboxylates are obtained by treatment of 2-O-trifluoromethanesulfonates (triflates) of either 1,4-or 1,5-lactones with acid in methanol; in some cases, very different tetrahydrofurans may result from acid or base treatment of a methanolic solution of the same starting material.