Alfonso Fernández-Mayoralas

Preparation of pyranoid glycal derivatives from phenyl thioglycosides and glycosyl phenyl sulphones

Abstract Phenyl thioglycopyranosides with various protecting groups (acetal, ether, ester) underwent reductive lithiation at C-1, followed by rapid elimination of the 2-substituent, when treated with lithium naphthalenide in tetrahydrofuran at low temperature. Thus, pyranoid glycal derivatives with acid-labile protecting groups were obtained in excellent yields. Glycopyranosyl phenyl sulphones were prepared quantitatively by oxidation of the corresponding phenyl thioglycosides with catalytic amounts of ruthenium trichloride in the presence of sodium periodate in a biphasic solvent system. These compounds also gave rise to pyranoid glycal derivatives in excellent yields when treated with lithium naphthalenide in tetrahydrofuran at low temperature. A β-linked 2′-deoxydisaccharide glycal derivative was also prepared from the corresponding disaccharide phenyl thioglycoside. Phenyl thioglycopyranosides carrying a 2-xanthate group underwent a radical reductive elimination when treated with tributyltin hydride, to afford glycal derivatives in good yields under neutral conditions.

Origins of the double asymmetric induction on proline-catalyzed aldol reactions.

Computational studies to elucidate the origin of the double asymmetric induction on proline-catalyzed aldol reaction have been performed using HF/6-31G(d) calculations. The computed transition structures explain the experimental data obtained.

Synthesis of 3- and 2′-fucosyl-lactose and 3,2′-difucosyl-lactose from partially benzylated lactose derivatives

Abstract O -β- d -Galactopyranosyl-(1→4)- O -[α- l -fucopyranosyl-(1→3)]- d -glucose has been synthesised by reaction of benzyl 2,6-di- O -benzyl-4- O -(2,3,4,6-tetra- O -benzyl-β- d -galactopyranosyl)-β- d -glucopyranoside with 2,3,4-tri- O -benzyl-α- l -fucopyranosyl bromide in the presence of mercuric bromide, followed by hydrogenolysis. Benzylation of benzyl 3′,4′- O -isopropylidene-β-lactoside, via tributylstannylation, in the presence of tetrabutylammonium bromide or N -methylimidazole, gave benzyl 2,6-di- O -benzyl-4- O -(6- O -benzyl-3,4- O -isopropylidene-β- d -galactopyranosyl)-β- d -glucopyranoside ( 6 ). α-Fucosylation of 6 in the presence of tetraethylammonium bromide provided either benzyl 2,6-di- O -benzyl-4- O -[6- O -benzyl-3,4- O -isopropylidene-2- O -(2,3,4-tri- O -benzyl-α- l -fucopyransoyl)-β- d - galactopyranosyl]-β- d -glucopyranoside ( 13 , 73%) or a mixture of 13 (42%) and benzyl 2,6-di- O -benzyl-4- O -[6- O -benzyl-3,4,- O -isopropylidene-2- O -(2,3,4-tri- O -benzyl-α- l -fucopyranosyl)-β- d - galactopyranosyl-3- O -(2,3,4-tri- O -benzyl-α- l -fucopyranosyl)-β- d -glucopyranoside ( 16 , 34%). α-Fucosylation of 13 in the presence of mercuric bromide and 2,6-di- tert -butyl-4-methylpyridine gave 16 (73%). Hydrogenolysis and acid hydrolysis of 13 and 16 afforded O -α- l -fucopyranosyl-(1→2)- O -β- d -galactopyranosyl-(1→4)- d -glucose and O -α- l -fucopyranosyl-(1→2)- O -β- d -galactopyranosyl-(1→4)- O -[α- l -fucopyranosyl-(1→3)]- d -glucose, respectively.

Inhibitors of Glioma Growth that Reveal the Tumour to the Immune System

Treated glioblastoma patients survive from 6 to 14 months. In the first part of this review, we describe glioma origins, cancer stem cells and the genomic alterations that generate dysregulated cell division, with enhanced proliferation and diverse response to radiation and chemotherapy. We review the pathways that mediate tumour cell proliferation, neo-angiogenesis, tumor cell invasion, as well as necrotic and apoptotic cell death. Then, we examine the ability of gliomas to evade and suppress the host immune system, exhibited at the levels of antigen recognition and immune activation, limiting the effective signaling between glioma and host immune cells. The second part of the review presents current therapies and their drawbacks. This is followed by a summary of the work of our laboratory during the past 20 years, on oligosaccharide and glycosphingolipid inhibitors of astroblast and astrocytoma division. Neurostatins, the O-acetylated forms of gangliosides GD1b and GT1b naturally present in mammalian brain, are cytostatic for normal astroblasts, but cytotoxic for rat C6 glioma cells and human astrocytoma grades III and I V, with ID50 values ranging from 200 to 450 nM. The inhibitors do not affect neurons or fibroblasts up to concentrations of 4 μM or higher. At least four different neurostatin-activated, cell-mediated antitumoral processes, lead to tumor destruction: (i) inhibition of tumor neo-vascularization; (ii) activation of microglia; (iii) activation of natural killer (NK) cells; (iv) activation of cytotoxic lymphocytes (CTL). The enhanced antigenicity of neurostatin-treated glioma cells, could be related to their increased expression of connexin 43. Because neurostatins and their analogues show specific activity and no toxicity for normal cells, a clinical trial would be the logical next step.

Convenient syntheses of substituted pyranoid glycals from thiophenyl glycosides and glycosyl phenylsulfones

Abstract A series of substituted thiophenyl glycosides and glycosyl phenylsulfones were converted in high yield into glycals after reductive lithiation with lithium naphthalenide, followed by elimination of the substituent at C-2.

The acetonation of lactose and benzyl β-lactoside with 2-methoxypropene

Abstract The acetonation of lactose with 2-methoxypropene afforded 4,6-O-isopropylidene lactose (2) and a diacetal which, after acetylation, gave an α,β-anomeric mixture of 1, 2,6,3-tetra-O-acetyl-3,2:4,6-di-O-isopropylidene lactose (4). Acetonation of benzyl b-lactoside afforded the mixed acetals benzyl 6,6-di-O-(methoxydimethyt)methyl (6), 6-O-(methoxydimethyl)methyl-(7) and 6-O-(methoxydimethyl) methyl-β -lactoside (8), the cyclic acetal benzyl 4,6-O-isopropylidene.-β-lactoside (9) and a diacetal which, after acetylation gave benzyl 2, 6, 3-tri-O-acetyl-3,2:4,6-di-O-isopropylidene-β-lactoside (11). The favoured formation of eight-membered 3,2-cyclic acetals in lactose derivatives has been further demonstrated by acetonation of benzyl 2,3,6-tri-O-benzyl-β-lactoside (13) and benzyl 2,6,3,6-tetra-O-benzyl-b-lactoside (12). As an example of the synthetic utility of this acetonation reaction, the chiral macrocyclic polyhydroxyether 25 has been synthesized from benzyl 3,4-O-isopropylidene-β-lactoside.

Synthesis of Antimitotic Thioglycosides: In Vitro and in Vivo Evaluation of Their Anticancer Activity

The synthesis and biological activity of oleylN-acetyl-α- and β-d-glucosaminides (1 and 2, respectively) and their thioglycosyl analogues (3 and 4, respectively) are reported. The compounds exhibited antimitotic activity on rat glioma (C6) and human lung carcinoma (A549) cell cultures in the micromolar range. Analysis of cell extracts using ultra performance liquid chromatography-mass spectrometry showed that the synthetic glycosides produce alterations in glycosphingolipid metabolism, with variable effect on the level of glucosylceramide depending on the configuration of the antimitotic used. In vivo experiments in nude mice bearing an implanted C6 glioma showed that the α-thioglycoside 3 reduced tumor volume, while the O-glycosyl derivative was inactive, highlighting the importance of using enzyme resistant glycosides.

Detection of Metabolite Changes in C6 Glioma Cells Cultured with Antimitotic Oleyl Glycoside by 1H MAS NMR

The synthetic glycoside, oleyl N-acetyl-alpha-D-glucosaminide (1), was previously shown to exhibit antimitotic activity on rat (C6) and human (U-373) glioma lines. To obtain information about its mechanism of action, metabolite changes in C6 glioma cells were analyzed after treatment with 1 using high-resolution magic angle spinning (1)H NMR. Compound 1 caused either a decrease or an increase in the intensity of the signal assigned to coenzyme A (CoA) metabolites depending on the concentration used. The data obtained from the (1)H NMR spectra of cells cultured with 1, combined with those obtained after treatment with oleic acid (an inhibitor of acetyl-CoA carboxylase) and phenyl butyrate (a known antineoplastic agent), suggest that 1 may be altering the metabolism of fatty acids and induce apoptosis of C6 glioma cells. These results point to NMR spectroscopy as an efficient technique for monitoring the response of the cells to therapeutic agents.

Noninvasive diagnosis of hypolactasia with 4-Galactosylxylose (Gaxilose): a multicentre, open-label, phase IIB-III nonrandomized trial.

Goals and Background: Hypolactasia affects over half of the world population. Diagnosis remains problematic as currently available tests, such as the hydrogen breath test, have low reliability and lactose intolerance symptoms are unspecific. We evaluated the diagnostic performance and safety of a new noninvasive diagnostic test based on urine or serum measurement of D-xylose after lactase cleavage of orally administered 4-galactosylxylose (gaxilose). Study: In a multicentre, open-label, nonrandomized, phase IIb-III study, consecutive patients with symptoms suggestive of lactose intolerance sequentially underwent intestinal biopsy for direct measurement of lactase activity (reference standard), hydrogen breath test, and blood glucose test after lactose challenge, 4- and 5-hour urine-based gaxilose test, and blood-based gaxilose test. For the gaxilose tests, 0 to 4 and 4 to 5 hours urine samples were taken after a 0.45 g gaxilose dose, whereas serum samples were taken 90 minutes after a 2.7 g dose for D-xylose determination. Genetic testing of hypolactasia was also assessed. Results: Of the 222 patients enrolled, 203 completed all diagnostic tests; 108 were hypolactasic according to biopsy. The sensitivities and specificities and positive and negative predictive values of the gaxilose tests were all >90% versus 69% to 85% for the hydrogen breath test and the blood glucose test. The area under the ROC curve was significantly higher for the gaxilose tests (>0.9, P⩽0.007). These tests also had higher sensitivity than genetic testing for hypolactasia and were well tolerated. Conclusions: The diagnostic performance of the gaxilose tests is excellent and can substantially improve the diagnosis of hypolactasia.

Phase i and phase IB clinical trials for the noninvasive evaluation of intestinal lactase with 4-galactosylxylose (gaxilose)

Goals and Background: Hypolactasia is widespread, yet reliable diagnostic tests are lacking. A new test based on oral administration of 4-galactosylxylose (gaxilose) and urine or serum measurement of D-xylose after cleavage by intestinal lactase is under clinical development. We investigated the optimal dose of gaxilose and calculate cutoff values of D-xylose for that dose. Study: In the randomized, dose-finding, phase I study, urine and serum pharmacokinetics of D-xylose were determined after oral administration of 6 ascending doses of gaxilose (and placebo) to 12 healthy adult volunteers. In the open, parallel, phase Ib study, 30 volunteers received the doses established for the urine and blood tests and D-xylose was measured. Cutoff values were calculated as 1.96×SD below the mean value. Safety was assessed through reporting of adverse events. Results: Gaxilose administration showed a progressive, dose-dependent increase in D-xylose in urine and serum. An optimal gaxilose dose of 0.45 g and urine collection periods of 4 and 5 hours were selected for further studies. For the blood test, a 2.7 g dose was selected and C max measured at 90 minutes. The calculated cutoff values of D-xylose for normal lactase activity were 27.58 and 37.87 mg for the 4- and 5-hour urine tests, respectively, and 0.97 mg/dL for the blood test. There were no treatment-related adverse events. Conclusions: The methodology described provides a simple, safe test for the evaluation of lactase activity in vivo. Further evaluation of the test as a noninvasive diagnosis of hypolactasia is ongoing in patients with lactose intolerance.