Alicia Fernández Cirelli

Gemini surfactants from alkyl glucosides

1,5-Bis-[6-O-(n-butyl α-d-glucopyranosid)] glutarate 7 was synthesized starting from d-glucose by a simple procedure. The anomeric mixture of alkyl glucosides was separated by flash chromatography of their peracetates. Detritylation in neutral conditions is described. This is the first example of a non ionic gemini surfactant where alkyl glucosides are linked through a spacer at C-6.

New dimeric surfactants from alkyl glucosides

Carbohydrate containing dimeric (or gemini) surfactants were synthesized starting from d-glucose. Three different spacers (glutaryl, succinyl and terephthaloyl) were used to link the sugar moieties through O-2 or O-6. The critical micellar concentration (CMC) for these new compounds was ten-fold smaller than that of their monomeric counterpart.

A gel-forming (1→3)-β-D-glucan isolated from cyttaria harioti fischer

Abstract An alkali-soluble glucan, [α] D + 11° ( M potassium hydroxide) having a degree of polymerization of 220, has been isolated from the fruit bodies of the tree fungus Cyttaria harioti Fischer. Periodate oxidation and methylation analysis show that it consists of a highly branched β- D -(1→3)-linked backbone. Hydrolysis of the methylated polysaccharide yielded 2,3,4,6-tetra- O -methyl- (24.5 mol%), 2,4,6-tri- O -methyl-(39.4 mol%), 2,3,4-tri- O -methyl- (8.6 mol%), and 2,4-di- O -methyl- D -glucose (27.5 mol%). Periodate-oxidation results substantiate the methylation studies. The general structural features of the glucan are discussed.

A suitable method for a rapid estimation of sulphated positions in polysaccharides of pharmacological interest

Abstract Most polysaccharides of pharmacological interest bear sulphate substituents. Methylation analysis is still a powerful method for structural elucidation. The butyllithium-methyl iodide procedure, previously reported for neutral glycans, has been applied to sulphated polysaccharides. Results obtained with heparin, heparan sulphates and synthetic derivatives of natural β-(1 → 3)-glucans show that it is a convenient method for the rapid estimation of sulphated positions.

β-elimination in aldonolactones. Synthesis of 2-deoxy-D-lyxo-hexose and 2-deoxy-D-arabino-hexose

Abstract Benzoylation of D -glycero- L -manno-heptono-1,4-lactone (1) with benzoyl chloride and pyridine for 2 h afforded crystalline penta-O-benzoyl- D -glycero- L -manno-heptono-1,4-lactone (2), but a large excess of reagent during 8 h also led to 2,5,6,7-tetra-O- benzoyl-3-deoxy- D -lyxo-hept-2-enono-1,4-lactone (3). Catalytic hydrogenation of 3 was stereoselective and gave 2,5,6,7-tetra-O-benzoyl-3-deoxy- D -galacto-heptono-1,4-lactone (4). Debenzoylation of 4 followed by oxidative decarboxylation with ceric sulfate in aqueous sulfuric acid gave 2-deoxy- D -lyxo-hexose (5). Application of the same reaction to 3-deoxy- D -gluco-heptono-1,4-lactone afforded 2-deoxy- D -arabino-hexose (6).

Effect of sulfation on the biological activity of β-(1→3)-glucans from the tree fungus Cyttaria harioti Fischer

Antitumor activity against Sarcoma 180 in mice has been reported for a fructoglucan isolated from Cyttaria johowii. This paper is concerned with the effect of sulfation on the antitumor activity of the alkali-soluble glucan (H-G) and its periodate oxidation-Smith-degradation product (H-L). The mitogenic responses of murine spleen cells to the sulfated glucans were also examined

Simple Stereocontrolled Synthesis of Methyl 2-Deoxy-d-erythro-hexopyranosid-4-uloses, Thromboxane B2 (TXB2) Precursors, from d-Galactose

Abstract The stereospecific synthesis of methyl 3-O-benzoyl-6-O-(tert-butyldiphenylsilyl)-2-deoxy-α-d-erythro-hexopyranosid-4-ulose (5) - a Thromboxane B2 (TXB2) precursor -starting from D-galactose is described. Facile and established methods including selective benzoylation, oxidation-elimination and a stereocontrolled hydrogenation (Pd/charcoal) were employed effectively.

Synthesis of crystalline derivatives of 3-deoxy-d-gluco-heptofuranose☆

Abstract Benzoylation of D -glycero- D -gulo-heptono-1,4-lactone afforded 2,3,5,6,7-penta-O-benzoyl- D -glycero- D -gulo-heptono-1,4-lactone, which, by 3-deoxygenation, gave 2,5,6,7-tetra-O-benzoyl-3-deoxy- D -gluco-heptono-1,4-lactone (4) in 80% overall yield. In a similar way, 2,5,6,7-tetra-O-acetyl-3-deoxy- D -gluco-heptono-1,4-lactone was prepared. Disiamylborane reduction of compound 4 gave crystalline 2,5,6,7-tetra-O-benzoyl-3-deoxy-β- D -gluco-heptofuranose (6), which was acetylated to give crystalline 1-O-acetyl-2,5,6,7-tetra-O-benzoyl-3-deoxy-β- D -gluco-heptofuranose (7). Upon treatment of 6 with diazomethane-boron trifluoride etherate, methyl 2,5,6,7-tetra-O-benzoyl-3-deoxy-β- D -gluco-heptofuranoside (8) was obtained. From the reaction mixture, the benzoylated β,β′-furanosyl disaccharide 11 was isolated. A higher yield (90%) of 8 was obtained by treatment of 7 with methanol and tin(IV) chloride. On O-debenzoylation of 8, methyl 3-deoxy-β- D -gluco-heptofuranoside was obtained. Compound 11 was the sole product (82% yield) when 6 was treated with boron trifluoride-etherate in dichloromethane. O-Debenzoylation of 11 afforded crystalline 3-deoxy-β- D -gluco-heptofuranosyl 3-deoxy-β- D -gluco-heptofuranoside. O-Debenzoylation of 6 with sodium methoxide in chloroform afforded crystalline 3-deoxy- D -gluco-heptose, whose tautomeric equilibrium was studied by 13C-n.m.r. spectroscopy.

β-Elimination in aldonolactones. Structure of the furan-2-one derivative obtained by benzoylation of D-glycero-D-gulo-heptono-1,4-lactone

Abstract A tri-unsaturated derivative, i. e. 3-benzoyloxy-5-(3-benzoyloxy-allylldene)-(5H)-furan-2-one ( 5 ), previously described as 3-benzoyloxy-5-(2-benzoyloxyallylidene)-(5H)-furan-2-one ( 3 ), was obtained from c per-O-benzoyl- D - C glycero- D - C gulo-heptono-1,4-lactone via β-elimination in basic conditions. Stereoespecific catalytic hydrogenation rendered 2,7-di- O -benzoyl-3,5,6-trideoxy-( DL )- threo -heptono-1,4-lactone ( 6 ). Structures 5 and 6 were assigned on the basis of spectral studies.

Chemical modification of glycosaminoglycans selective 2-sulfation of d-glucuronic acid units in heparan sulfate

Abstract O -Sulfation of heparan sulfate was performed in conditions that minimise N -desulfation. NMR spectra and methylation analysis of sulfated heparan sulfate confirmed the selective substitution at O-2 of glucuronic acid units.