Synthesis of three natural diosgenyl glycosides.

Three well-known natural diosgenyl glycosides which have the same sugar chains but different sequence, ophipogonin C', polyphillin C and prosapogenin B, were synthesised by a facile approach. A method using the levulinyl group as a protecting group to selectively mask the C3-OH of diosgenyl 4,6-O-benzylidene-beta-D-glucopyranoside is described.

Reduced endothelial nitric oxide synthase in lungs of chronically ventilated preterm lambs.

Nitric oxide (NO), produced in lung vascular endothelium and airway epithelium, has an important role in regulating smooth muscle cell growth and tone. Chronic lung disease, a frequent complication of premature birth, is characterized by excess abundance, tone, and reactivity of smooth muscle in the pulmonary circulation and conducting airways, leading to increased lung vascular and airway resistance. Whether these structural and functional changes are associated with diminished pulmonary expression of endothelial nitric oxide synthase (eNOS) protein is unknown. Both quantitative immunoblot analysis and semiquantitative immunohistochemistry showed that there was less eNOS protein in the endothelium of small intrapulmonary arteries and epithelium of small airways of preterm lambs that were mechanically ventilated for 3 wk compared with control lambs born at term. No significant differences were detected for other proteins (inducible NOS, alpha-smooth muscle actin, and pancytokeratin). Lung vascular and respiratory tract resistances were greater in the chronically ventilated preterm lambs compared with control term lambs. These results support the notion that decreased eNOS in the pulmonary circulation and respiratory tract of preterm lambs may contribute to the pathophysiology of chronic lung disease.

Acute renal failure: unusual complication of Epstein-Barr virus-induced infectious mononucleosis.

A 17-year-old boy with juvenile rheumatoid arthritis presented with jaundice, confusion, hemolytic anemia, thrombocytopenia, and acute renal failure secondary to titer-confirmed acute Epstein-Barr virus (EBV). Renal biopsy specimen revealed interstitial nephritis with an inflammatory infiltrate composed of cytotoxic/suppressor T cells, and interstitial mononuclear cell nuclei expressed EBV encoded RNA-1 (EBER-1) mRNA. Methylprednisolone treatment resulted in rapid improvement.

Synthesis of a 3-deoxy-L-iduronic acid containing heparin pentasaccharide to probe the conformation of the antithrombin III binding sequence.

We report in this work the total synthesis of a close analogue of the pentasaccharide active site of heparin, in which the L-iduronic acid residue has been deoxygenated at position three. 1H NMR studies demonstrated that, as anticipated, such a modification induces a shift of the conformational equilibrium toward 1C4 (contribution to the conformational equilibrium rises from 37% to 65%) and a substantial decrease of the affinity for antithrombin III (Kd 0.154 microM versus 0.050 microM).

Inhibition of GPI phospholipase C from Trypanosoma brucei by fluoro-inositol dodecylphosphonates.

Glycosyl phosphatidylinositol phospholipase C (GPI-PLC) of Trypanosoma brucei is inhibited by myo-inositol(Ins)-1-O-dodecylphosphonate (VP-602L). Several novel fluoro-substituted analogs of 2-deoxy-myo-Ins-1-O-dedecylphosphonate, among which 2-deoxy-2-fluoro-scyllo-Ins-1-O-dodecylphosphonate (VP-616L) was the most powerful, were shown to be competitive inhibitors of GPI-PLC. VP-616L was 14-fold more active than VP-602L. 2-Deoxy-2-fluoro-myo-Ins-1-O-dodecylphosphonate and 2-deoxy-2,2-difluoro-myo-Ins-1-O-dodecylphosphonate were 1.55- and 4.67-fold, respectively, more potent than VP-602L. Methyl 2-deoxy-2,2-difluoro-myo-Ins-1-O-dodecylphosphonate did not inhibit GPI-PLC. These observations provide several insights into how GPI-PLC might interact with its substrate at the active site. We surmise that (i) the 2-OH of Ins is probably dispensable for substrate recognition; (ii) an equatorially oriented active site residue might interact with substituents at the 2-position of Ins, and (iii) the negative charge on the phosphoryl at the 1-OH position of Ins might be important for substrate recognition.

Synthesis of eight glycosides of hexasaccharide fragments representing the terminus of the O-polysaccharide of Vibrio cholerae O:1, serotype Inaba and Ogawa, bearing aglycons suitable for linking to proteins.

The title substances were prepared from intermediate, fully acetylated alpha-trimethylsilylethyl (SE) glycosides. The latter were assembled in a blockwise manner, using as the glycosyl donor the alpha-glycosyl chloride of a disaccharide bearing two 4-azido-4-deoxy functions. Next, the azido groups in the assembled hexasaccharides were converted to the corresponding amines, and these were acylated with 4-O-benzyl-3-deoxy-L-glycero-tetronic acid in the presence of a water-soluble carbodiimide. The SE glycosides were then transformed to glycosyl imidates, and these were coupled with methyl 6-hydroxyhexanoate or methyl 2-(2-hydroxyethylthio) propionate. The aglycons in the glycosides thus obtained were then converted to the corresponding carboxylic acids or acyl hydrazides. Such compounds are suitable for linking to proteins to obtain neoglycoproteins.

Synthesis of the methyl alpha-glycoside of a trisaccharide mimicking the terminus of the O antigen of Vibrio cholerae O:1, serotype Inaba.

Coupling of methyl 4-amino-4,6-dideoxy-2-O-4-methoxybenzyl-alpha-D-mannopyranoside, obtained from the corresponding 4-azido derivative by treatment with H2S, with 3-deoxy-L-glycero-tetronolactone gave the crystalline methyl 4-(3-deoxy-L-glycero-tetronamido)-4,6-dideoxy-2-O-4-methoxybenzyl- alpha-D- mannopyranoside (7). Subsequent acetylation of 7, followed by O-demethoxybenzylation of the 8 formed gave the crystalline methyl 3-O-acetyl-4,6-dideoxy-4-(2,4-di-O-acetyl-3-deoxy-L-glycero-tetronami do)-alpha- D-mannopyranoside (9), which was used as the key intermediate in the construction of the title trisaccharide. To make a glycosyl donor allowing the extension of the oligosaccharide chain at O-2, compound 9 was converted, via conventional transformations, into 3-O-acetyl-2-O-bromoacetyl-4,6-dideoxy-4-(2,4-di-O-acetyl-3-deoxy-L-glyc ero- tetronamido)-alpha-D-mannopyranosyl chloride (12). Condensation of 12 with 9 afforded the disaccharide 20 having a selectively removable protecting group at O-2(2). The latter was O-debromoacetylated, and the disaccharide nucleophile thus obtained was treated with 2,3-di-O-acetyl-4,6-dideoxy-4-(2,4-di-O-acetyl-3-deoxy-L-glycero-tetr onamido)- alpha-D-mannopyranosyl chloride to give, after O-deacetylation, the target, title trisaccharide. The constituent monosaccharide of the O-specific polysaccharide antigen of Vibrio cholerae serotype Inaba, 4-(3-deoxy-L-glycero-tetronamido)-4,6-dideoxy-D-mannopyranose (18), was obtained from the peracetate of its methyl alpha-glycoside by acetolysis, followed by O-deacetylation. The amorphous compound 18 was characterized by 1H and 13C NMR spectroscopy and through its crystalline alpha-per-O-acetyl derivative.

Synthesis and crystal structure of methyl 4-6-dideoxy-4-(3-deoxy-L- glycero-tetronamido)-2-O-methyl-alpha-D-mannopyranoside, the methyl alpha-glycoside of the terminal unit, and presumed antigenic determinant, of the O-specific polysaccharide of Vibrio cholerae O:1, serotype Ogawa.

Methyl 4-azido-4,6-dideoxy-3-O-benzyl-alpha-D-mannopyranoside and its analogous 3-O-(4-methoxybenzyl) derivative were methylated and the 2-O-methyl derivatives formed were converted into methyl 4-amino-4,6-dideoxy-2-O-methyl-alpha-D- mannopyranoside [sequence: see text]. Reaction of the latter with 3-deoxy-L-glycero-tetronolactone gave the methyl glycoside of 4,6-dideoxy-4-(3-deoxy-L-glycero- tetronamido)-2-methyl-alpha-D-mannopyranose [sequence: see text], the monosaccharide that is reported to be the terminal moiety of the O-specific polysaccharide of Vibrio cholerae O:1, serotype Ogawa. The unit cell packing of the compound, which crystallized as a monohydrate, differs from that of the previously described crystalline compound lacking the 2-O-methyl group. The unmethylated sugar is the terminal moiety of the O-specific polysaccharide of Vibrio cholerae O:1, serotype Inaba. The crystal structure of methyl 4,6-dideoxy-2-O- methyl-4-trifluoroacetamido-alpha-D-mannopyranoside [sequence: see text] is also described.