Struktur von sechs Coleonen (Diterpenen) aus Solenostemon monostachys (P. BEAUV.) BRIQ. (Labiatae)

Structures of Six Coleons (Diterpenoids) from Solenostemon monostachys (P. BEAUV .) BRIQ . (Labiatae) The above mentioned African labiate has been investigated for its leaf-gland pigments. Besides the already known coleons C ( 1 ) and H ( 2 ), 2a-formoxy-coleon C ( 3 ), 12β-O-acetyl-coleon Z ( 7 ), 12β-O-acetyl-7-O-formyl-7-O-desacetyl-coleon Z ( 8 ) and a not separated mixture of 17-acetoxy-12β-O-acetyl-coleon Z ( 9a ) and 12β-O-acetyl-17-formoxy-coleon Z ( 9b ) have been isolated.     

Synthesis of Methyl 2-Acetamido-4,6-di-O-acetyl-3-S-acetyl-2-deoxy-3-thio-α-D-mannopyranoside

Methyl-2-acetamido-4,6-di-O-acetyl-3-S-acetyl-2-deoxy-3-thio-α-D-mannopy-ranoside has been synthesized by conversion of methyl 2-amino-2-deoxy-4,6-O-benzylidene-α-D-altropyranoside into the corresponding 3-O-methanesulfony1-2-N-[(methylthio)thiocarbonyl]derivative followed by intramolecular displacement of the 3-O-methanesulfonyloxy group with the (methylthio)thiocarbamoyl group.     

Über Pterinchemie. 85. Mitteilung. Polyacetylierte 5,6,7,8-Tetrahydro-D- und -L-neopterine. Ein besonderer Fall von N(5)-Alkylierung des 5,6,7,8-Tetrahydroneopterin-Gerüstes

Polyacetylated 5,6,7,8-Tetrahydro-D - and L -neopterins. A Special Case of N(5)-Alkylation of 5,6,7,8-Tetrahydroneopterins Improved conditions are reported for the preparation of the earlier described (6R)- and (6S)-1′-O,2′-O,3′-O,2-N,5-pentaacetyl-5,6,7,8-tetrahydro-L -neopterins, one of which could be obtained as pure crystals. Its structure, determined by X-ray-diffraction analysis, corresponds to the (6R)-enantiomer. The method has also been used to make the corresponding D -diastereoisomers. Further acetylation of (6RS)-1′-O,2′-O,3′-O,2-N-tetraacetyl-5,6,7,8-tetrahydro-D -neopterin under drastic conditions yields a mixture of several polyacetylated D -neopterin derivatives and a polyacetylated ethyl-tetrahydro-D -neopterin which was isolated in crystalline form and established by X-ray-diffraction analysis to be (6R)-1′-O,2′-O,3′-O,4-O,2-N,2-N,8-heptaacetyl-5-ethyl-5,6,7,8-tetrahydro-D -neopterin.     

Stereochemical differentiation and simultaneous analysis of 3-, 4-, and 5-hydroxyalkanoic acids from biopolyesters by multidimensional gas chromatography

The direct enantioselective analysis of 3-, 4-, and 5-hydroxy fatty acids from biological material has been achieved by enantioselective multidimensional gas chromatography (enantio-MDGC) with heptakis(2,3-di-O-methyl-6-O-tert-butyldimethylsilyl)- or (2,3-di-O-acetyl-6-O-tert-butyldimethylsilyl)-β-cyclodextrin as chiral stationary phase. All the bacteria investigated produced polyesters of enatiomerically pure (R) configured compounds.     

Modifications at the 6-O-position of 1-deoxynojirimycin: facile and efficient synthesis of 6-O-alkylated-N-octyl-1-deoxynojirimycin derivatives

A straightforward synthesis of N-alkylated 1-deoxynojirimycin derivatives modified at the 6-O-position has been described. The key intermediate in the synthesis of target compounds was 2,3,4-tri-O-benzyl-1,5-dideoxy-1,5-imino-D-glucitol, which was prepared from 2,3,4,6-tetra-O-benzyl-1,5-dideoxy-1,5-imino-D-glucitol. Optimal conditions have been established for the synthesis of the key intermediate by varying reaction parameters. Reductive amination and subsequent alkylation of the 6-O-position followed by hydrogenolysis were the main reaction steps, which gave target compounds 6-O-ethyl-N-octyl-1,5-dideoxy-1,5-imino-D-glucitol and 6-O-butyl-N-octyl-1,5-dideoxy-1,5-imino-D-glucitol. This synthetic route is flexible and can be useful for the synthesis of other lipophilic iminosugar derivatives.     

Contribution à la phytochimie du genre Gentiana. XXVI.. Identification d'une nouvelle di-O-glucosyl cinnamoyl-C-glucosylflavone extraite des feuilles de Gentiana X marcailhouana RY.

Phytochemistry of Genus Gentiana. XXVI. Identification of a New Di-O-glucosyl Cinnamoyl-C-glucosylflavone in the Leaves of Gentiana X marcailhouana RY . A new di-O-glucosyl cinnamoyl-C-glucosylflavone has been identified as 4′-O-β-D -glucosyl-2″-O-[2-O-β-D -glucosyl-2,4,5-trihydroxy-(E)-cinnamoyl]isoorientin ( 1 ).     

Separation of Flavonoids from the Leaves of Oroxylum indicum by HSCCC

A high-speed counter-current chromatography system (HPCCC) capable of rapid processing has been employed to separate seven flavonoids from a methanolic extract of the leaves of Oroxylum indicum by a one-step isocratic elution using a chloroform–methanol–water (9.5:10:5) two-phase system. LC, MS and NMR have identified the components from the extract as chrysin, baicalein, baicalein-7-O-glucoside, baicalein-7-O-diglucoside, chrysin-7-O-glucuronide, baicalein-7-O-glucuronide, and a chrysin-diglucoside. Baicalein-7-O-glucuronide and chrysin-7-O-glucuronide have been separated from this plant by HSCCC for the first time. The present study also reports a new chrysin-diglucoside from the leaf extract. The results demonstrate that HSCCC is a powerful separation tool and can contribute to identifying and quantifying plant ingredients.

     

Synthesis of novel macrocyclic crown ethers from D-glucose

A simple and efficient synthetic protocol for an easy access of carbohydrate-linked crown ethers from cheap and readily available D-glucose in good yields has been devised. The base-mediated cyclization of sugar-linked bis-iodo podands in CH₃CN with amines, including ethylamine and furfurylamine afforded the novel chiral monoaza-15-crown-5-type macrocyclic crown ethers anellated to 3-O-benzyl-1,2-O-isopropylidene-α-D-glucofuranose and 3-O-benzyl-1,2-O-isopropylidene-α-D-allofuranose. The glucose-based crown ethers have been characterized by spectroscopy techniques including IR, ¹H NMR, and ¹³C NMR.     

Apolipoprotein E Recognizes Alzheimer's Disease Associated 3-O Sulfation of Heparan Sulfate

Apolipoprotein E (ApoE)’s ϵ4 alle is the most important genetic risk factor for late onset Alzheimer's Disease (AD). Cell-surface heparan sulfate (HS) is a cofactor for ApoE/LRP1 interaction and the prion-like spread of tau pathology between cells. 3-O-sulfo (3-O-S) modification of HS has been linked to AD through its interaction with tau, and enhanced levels of 3-O-sulfated HS and 3-O-sulfotransferases in the AD brain. In this study, we characterized ApoE/HS interactions in wildtype ApoE3, AD-linked ApoE4, and AD-protective ApoE2 and ApoE3-Christchurch. Glycan microarray and SPR assays revealed that all ApoE isoforms recognized 3-O-S. NMR titration localized ApoE/3-O-S binding to the vicinity of the canonical HS binding motif. In cells, the knockout of HS3ST1-a major 3-O sulfotransferase-reduced cell surface binding and uptake of ApoE. 3-O-S is thus recognized by both tau and ApoE, suggesting that the interplay between 3-O-sulfated HS, tau and ApoE isoforms may modulate AD risk.     

Syntheses of O-(2-Acetamido-2-Deoxy-α-D-Galactopyranosyl)-Myo-Inositols

ABSTRACT

The structure of an O-(2-acetamido-2-deoxy-α-D-galactopyranosyl)-myo-inositol isolated from human pregnancy urine has previously been identified as that of 1-O-(2-acetamido-2-deoxy-α-D-galactopyranosyl)-myo-inositol. In order to ascertain the absolute configuration in the inositol part of the compound, the 1D- and 1L- isomers were synthesised. Since none of these two stereoisomers corresponded to the natural product, the corresponding 2-O-, the mixture of the two 1DL-4-O-, and 5-O- isomers were also synthesised. None of these gave ¹H NMR spectra corresponding to the natural product, the structure of which therefore remains unresolved.     

Synthesis of A Novel Sialyl Lewis X Analogue Containing A Pyrrolidine in Place of N-Acetyl Glucosamine

ABSTRACT

The synthesis of the new sialyl Lewis X analogue, 4-O-(α-L-fucopyranosyl)-3-O-(3-O-sodium sulfonato-β-D-galactopyranosyl)-(2S,3R, 4R)-2-ethyl-3,4-dihydroxypyrrolidine 2 has been achieved. The N-acetyl glucosamine unit of natural Lewis X has been replaced by a rigid 3R/4R-dihydroxylated pyrrolidine 12. This one has been synthezised from the methyl 4-O-benzoyl-2,3-di-O-benzyl-6-deoxy-6-iodo-α-D-altropyranoside sugar precursor 10 using the Ganem/Bernotas one-pot elimination-reductive amination ring contraction reaction. The (2S, 3R, 4R)-1-benzyloxycarbonyl-3,4-dihydroxy-2-ethylpyrrolidine 12 obtained was subsequently regioselectively glycosylated, using 2,3,4-tri-O-benzyl-α-L-fucopyranosyl fluoride and 2,3,4,6-tetra-O-benzoyl-β-D-galactopyranosyl bromide as glycosyl donors. Disaccharide containing pyrrolidine 21 was finally transformed into the target O-sulfated analog 2, after regioselective sulfation and usual deprotection.     

Convenient Synthesis of 2-Deoxy-D-Glucofuranosides

ABSTRACT

Methyl 2-deoxy-D-glucofuranoside has been conveniently prepared starting from 3-O-benzyl-1,2-O-isopropylidene-α-D-glucofuranose, involving the first described deoxygenation at the 2-position.     

Dérivés du C-méthyl-3-xylofurannose

3-C-Methylxylofuranose Derivatives 3′-C-methyladenosine has been known for almost ten years whereas its 3′-epimer is still to be prepared, because of the difficulty of synthesizing the 3-C-methylxylo-furanose. In this communication, the synthesis of 1,2-O-isoproypylidene acetal 9 and its derivatives is described. Vicinal dihydroxylation of 5-O-benzoyl-3-deoxy-1,2-O-isopryopylidene-3-C-methylidene-α-D -erythro-pentofuranose ( 6 ) led to the branchedchain sugar derivative 7 which was selectively tosylated to 8 whose reduction gave 9 . These reactions, as well as the derivatizations of 7 , 8 and 9 , took place with good to excellent yields.     

A New Pyranocoumarin Diester from Polygala paniculata L

A new coumarin diester has been isolated from Polygala paniculata L. (Polygalaceae) by a combination of flash chromatography on silica gel and preparative reversed-phase chromatography. Its structure has been determined as 3′-O-acetyl-4′-O-benzoylkhellactone (= 9-acetoxy-9,10-dihydro-8,8-dimethyl-2-oxo-2 H,8H-benzo[1,2-b:3,4-b′]dipyranh-10-yl benzoate) by spectroscopic methods (UV, IR, ¹H-NMR, EI-and CI-MS) and by X-ray analysis.     

Synthesis Of Ligands Related To The O-Specific Antigen Of Shigella Dysenteriae Type 1.

Abstract

Stereoselective α-D-galactosylation at the position 3 of 4,6-O-substituted derivatives of methyl 2-acetamido-2-deoxy-α-D-glucopyranoside is described. Glycosyl chlorides derived from 3,4,6-tri-O-acetyl-2-O-benzyl- and 2-O-(4-methoxybenzyl)-D-galactopyranose have been used as glycosyl donors. Methyl 2-acetamido-4,6-di-O-acetyl-2-deoxy-3-O-(3,4,6-tri-O-acetyl-α-D-galactopyranosyl)-α-D-glucopyranoside (27) and methyl 2-acetamido-4,6-di-O-benzyl-2-deoxy-3-O-(3,4,6-tri-O-acetyl-α-D-galactopyranosyl)-α-D-glucopyranoside (31) have been prepared.     

Cyclodextrin derivatives for GC separation of racemic mixtures of volatile compounds. Part VIII: 2,6-di-O-methyl-3-O-pentyl-γ-cyclodextrin and 2,6-di-O-methyl-3-O-(4-oxo-pentyl)- and 2,6-di-O-pentyl-3-O-(4-oxo-pentyl)-β-and -γ-cyclodextrins

In pre vious papers, 2,6-di-O-methyl-3-O-pentyl-β-cyclodextrin (CD) was demonstrated to be successful in separating volatile compounds, while avoiding the drawbacks of 2,3,6-tri-O-methyl-O-methyl-β-CD in terms of column stability and operating temperature. Since a CD chiral selector of universal use has not yet been found, and at least two (or more) columns coated with different CD derivatives are therefore necessary for routine work, the performance of 2,6-di-O-methyl-3-O-pentyl-γ-CD, 2,6-di-O-methyl-3-O-(4-oxopentyl)-γ-CD, 2,6-di-O-pentyl-3-O-(4-oxo-pentyl)-β-CD, and 2,6-di-O-pentyl-3-O-(-4-oxo-pentyl)-γ-CD diluted in polysiloxanes for the separation of volatile compounds in aromas and essential oils will be illustrated; each column coated with each of the newly synthesized CD derivatives was evaluated by analyzing more than 150 different recemates with different structures.     

Structure Elucidation and Synthesis of Flavonol Acylglycosides. III.. The synthesis of tiliroside

Naturally occurring kaempferol 3-O-β-D -(6″-O-coumaroyl)glucopyranoside (tiliroside) has been synthesized thereby confirming its structure. This is the first acylated flavonoid glycoside to be synthesized.     

Two new sucrose esters from the rhizome of Sparganium stoloniferum Buch.-Ham.

Two new sucrose esters, β-D-(1-O-acetyl-3,6-O-trans-diferuloyl)fructofuranosyl-α-D-2′-O-acetylglucopyranoside (1) and β-D-(1-O-acetyl-3-O-cis-feruloyl-6-O-trans-feruloyl)fructofuranosyl-α-D-2′,4′,6′-O-triacetylglucopyranoside (2), together with four known sucrose esters (3–6) have been isolated from the rhizome of Sparganium stoloniferum Buch.-Ham. Their structures were elucidated by physical and chemical evidence and spectral analysis.     

19-O-Acetylchaetoglobosin B and 19-O-Acetylchaetoglobosin D,Two New Metabolites of Chaetomium globosum

Two new metabolites have been isolated from cultures of Chaetomium globosum. The structures of 19-O-acetylchaetoglobosin B ( 4 ) and 19-O-acetylchaetoglobosin D ( 5 ) are assigned. The ¹³C-NMR. spectra of chaetoglobosin A ( 1 ), 19-O-acetylchaetoglobosin A ( 2 ), chaetoglobosin C ( 3 ), 19-O-acetylchaetoglobosin B ( 4 ), 19-O-acetylchaetoglobosin D ( 5 ) and of cytochalasin G ( 6 ), a (3-indolyl)-[11]cytochalasan isolated from Pseudeurotium zonatum, have been interpreted.