Struktur und synthese von flavonol-triosiden aus rhamnus-arten

By synthesis and ¹³C-NMR spectroscopic investigations of rhamnocitrin-, rhamnazin- and rhamnetin - 3 - O - [O - α - l - rhamnopyranosyl - (1 → 4) - O - α - l - rhamnopyranosyl - (1 → 6)] β - d - galactopyranosides and of rhamnocitrin - 3 - O - [O - α - l - rhamnopyranosyl - (1 → 3) - O - α - l - rhamnopyranosyl - (1 → 6)] - β - d - galactopyranoside (rhamnocitrin - 3 - O - β - rhamnisoide) it was proved that all naturally occurring flavonoltriosides, so far isolated from different Rhamnus species, contain the sugar-moiety rhamninose. Thus it was shown that catharticin (rhamnocitrin - 3 - O - β - rhamninoside) is identical with alaternin and xanthorhamnin A (rhamnetin - 3 - O - β - rhamninoside) with xanthorhamnin B, whereas xanthorhamnin C is rhamnazin - 3- O - β - rhamninoside. From Rhamnus saxatilis JACQ., ssp. saxat. a new flavonol - acetyl - trioside was isolated and the structure by MS and ¹³C-NMR spectroscopic means elucidated to be the rhamnetin - 3 - O - [O - α - l - rhamnopyranosyl - (1 → 3) - O - (4 - O - acetyl - ) - α - l - rhamnopyranosyl - (1 → 6)] - β - d - galactopyranoside.     

Synthesis of a d,d- and l,d-heptose-containing hexasaccharide corresponding to a structure from Haemophilus ducreyi lipopolysaccharides

The synthesis of a linear hexasaccharide, 2-(4-trifluoroacetamidophenyl)ethyl (β-d-galactopyranosyl)-(1→4)-(2-acetamido-2-deoxy-β-d-glucopyranosyl)-(1→3)-(β-d-galactopyranosyl)-(1→4)-(d-glycero-α-d-manno-heptopyranosyl)-(1→6)-(β-d-glucopyranosyl)-(1→4)-l-glycero-α-d-manno-heptopyranoside, corresponding to a structure found in Haemophilus ducreyi LPS, is described. A Barbier reaction between benzyloxymethyl chloride and a properly protected 6-aldo-1-thio-mannopyranoside yielded both the d,d- and the l,d-heptopyranoside (2 and 3, ratio 2:3), which were separated and both used in the synthesis. p-Methoxybenzyl and chloroacetyl groups were employed as temporary protecting groups, selectively removed in the presence of the persistent benzyl, acetyl, benzoyl and isopropylidene groups by treatment with DDQ/H₂O and hydrazine dithiocarbonate, respectively. Thioglycosides were utilised as donors throughout using either NIS/TfOH or DMTST as promoters. The introduction of the spacer into thioglycoside 5 was high-yielding (95%) but with low stereoselectivity (α:β 5:3). All other glycosylations are completely stereoselective. The target hexasaccharide is obtained via a 3+3 block approach with the yield in the final NIS/TfOH-promoted coupling between an N,N-diacetyl-trisaccharide thioglycosyl donor 20 and a 4′′-OH trisaccharide acceptor 13 being 75%.     

Synthese d'oligosaccharides sur polymere support—IV : Reactions sur polymere “popcorn”

The different steps leading to oligosaccharide synthesis on polymeric support have been studied in the case of a functionalized ”popcorn” polystyrene: anchoring of the first glucidic group, unblocking of a selectively protected hydroxyl group, glycosylation and cleavage of the glucide support bond. The first glucidic unit is attached by a benzoic ester bond cleaved by methanolysis (Zemplén's method); β-benzoylpropionic ester was used as temporary protecting group. The synthesis of benzyl - 2 - acetamido - 4,6 - di - O - acetyl - 3 - O - (2 - acetamido - 3,4,6 - tri - O - acetyl - 2 - deoxy - β - D - glucopyranosyl) - 2 - deoxy - α - D - glucopyranoside is described as an example.     

Synthesis of an analogue of the polyoxins: X-ray structure of starting carbohydrate and acetal migration accompanying acetolysis

An analogue of the polyoxins has been prepared from 1,5 - di - O - acetyl - 3 - C - (R) - ethoxycarbonylmethyl -5(R),1′(R) - N - formylepimino - 2,3 - O - isopropylidene - β - d - ribofuranose (13). The structure of 13 was determined by X-ray analysis. Intramolecular acetal migrations were observed during acetolysis under acid conditions.     

O,O-dialkylphosphoroselenoic acids as functionalising reagents of monosaccharides—III: A novel synthesis of unsaturated sugars by eoxygenation of sugar epoxides with dialkylphosphoroselenoic acids

Sugar epoxides are transformed in almost quantitative yields, under mild reaction conditions, into their corresponding unsaturated monosaccharides by reaction with O,O-dialkylphosphoroselenoic acids salts. A mechanism involving the formation of a penta-coordinate phosphorus intermediate is proposed.The deoxygenation was performed with the following sugar epoxides: 5,6 - anhydro -1,2 - O - isopropylidene - α - D - glucofuranose (1), 5,6 - anhydro - 1,2 - O - cyclohexylidene - α - D - glucofuranose (2), methyl - 2,3 - anhydro - 4, 6 - O - benzylidene - α - D - allopyranoside (3), methyl - 2,3 - anhydro - 4,6 - O - benzylidene - α - D - mannopyranoside (4) and 3,4,6 - tri - O - acetyl - 1,2 - anhydro - α - D - glucopyranose (Brigl's anhydride) (5).     

Synthesis of Cryptococcus neoformans Capsular Polysaccharide Structures. IV. Construction of Thioglycoside Donor Blocks and Their Subsequent Assembly

Di‐ and trisaccharide thioglycoside building blocks, ethyl (2,3,4‐tri‐O‐benzyl‐β‐d‐xylopyranosyl)‐(1→2)‐3‐O‐allyl‐4,6‐di‐O‐benzyl‐1‐thio‐α‐d‐mannopyranoside, ethyl (2,3,4‐tri‐O‐benzyl‐β‐d‐xylopyranosyl)‐(1→2)‐6‐O‐acetyl‐3‐O‐allyl‐4‐O‐benzyl‐1‐thio‐α‐d‐mannopyranoside and ethyl (2,3,4‐tri‐O‐benzyl‐β‐d‐xylopyranosyl)‐(1→4)‐[(2,3,4‐tri‐O‐benzyl‐β‐d‐xylopyranosyl)‐(1→2)]‐3‐O‐allyl‐6‐O‐benzyl‐1‐thio‐α‐d‐mannopyranoside, corresponding to repetitive structures in the capsular polysaccharide (CPS) of Cryptococcus neoformans have been synthesised using silver triflate‐promoted couplings between benzobromoxylose and properly protected mannose ethyl thioglycosides. The blocks contain an orthogonal allyl group in the 3‐position of the mannose residue to allow continued formation of the (1→3)‐linked mannan backbone of the CPS. They have benzyl ethers as persistent protecting groups to facilitate access to the acetylated target structures. Assembly of the blocks employing DMTST as promoter in diethyl ether afforded in high yield and complete stereoselectivity penta‐ and hexasaccharide motifs from C. neoformans serotype A–C. The latter were deallylated into new acceptors to allow synthesis of larger CPS‐fragments.     

Synthesis of benzyl O-(2,3,3'-tri-O-acetyl-β-D-apiofuranosyl)-(1→3)-2,4-di-O-benzoyl-α-D-xylopyranoside and its X-ray structure

The protected apiose-containing disaccharide, benzyl O-(2,3, 3'-tri-O-acetyl-β-D-apiofuranosyl)-( 1→3)-2, 4-di-O-benzoyl-α-D-xylopyranoside, was synthesized and its X-ray structure provided.     

Approche de la synthese d'anthracyclines oligosaccharidiques. Hemisynthese de la 4'-o-(2-desoxy l-fucosyl) daunorubicine

The preparation of the disaccharide 4 - O - (3,4 - di - O - acetyl - 2,6 - dideoxy - α - l - lyxo - hexopyranosyl) - 2, 3,6 - trideoxy - 3 - trifluoroacetamido - l - lyxo - hexopyranose, 11c, the N,N' - dimethyl derivative of which occurs naturally in numerous anthracyclines, is described. Glycosidation with daunomycinone followed by removal of the protecting groups led to 4' - O - (2 - deoxy - l - fucosyl) daunorubicine.     

Synthesis of Cryptococcus neoformans Capsular Polysaccharide Structures. Part V: Construction of Glucuronic Acid‐Containing Thioglycoside Donor Blocks

Abstract

Glucuronic acid‐containing di‐ and trisaccharide thioglycoside building blocks, ethyl (benzyl 2,3,4‐tri‐O‐benzyl‐β‐D‐glucopyranosyluronate)‐(1 → 2)‐3‐O‐allyl‐4,6‐di‐O‐benzyl‐1‐thio‐α‐D‐mannopyranoside, ethyl (benzyl 2,3,4‐tri‐O‐benzyl‐β‐D‐glucopyranosyluronate)‐(1 → 2)‐6‐O‐acetyl‐3‐O‐allyl‐4‐O‐benzyl‐1‐thio‐α‐D‐mannopyranoside and ethyl (2,3,4‐tri‐O‐benzyl‐β‐D‐xylopyranosyl)‐(1 → 4)‐[(benzyl 2,3,4‐tri‐O‐benzyl‐β‐D‐glucopyranosyluronate)‐(1 → 2)]‐3‐O‐allyl‐6‐O‐benzyl‐1‐thio‐α‐D‐mannopyranoside, corresponding to repetitive structures in the capsular polysaccharide (CPS) of Cryptococcus neoformans, have been synthesized. The blocks contain an orthogonal allyl group in the 3‐position of the mannose residue to allow formation of the (1 → 3)‐linked mannan backbone of the CPS and benzyl ethers as persistent protecting groups to facilitate access to acetylated target structures. The glucuronic acid moiety was introduced using an acetylated trichloroacetimidate donor and the xylose residue employing the benzoylated bromo sugar to ensure β‐selectivity in the couplings. Exchange to benzyl protecting groups was then performed at the di‐ or trisaccharide level. Assembly of suitable blocks employing DMTST as promoter in diethyl ether then afforded, in high yield and with stereoselectivity, a protected pentasaccharide corresponding to a C. neoformans serotype D CPS structure.     

Crystal structures of methyl and benzyl 5-ferrocenyl-3,5-dimethyl-2-pyrazoline-1-dithiocarboxylate

Reactions of E-4-ferrocenylpent-3-en-2-one with S-methyldithiocarbazate or S-benzyldithiocarbazate result in the formation of methyl 5-ferrocenyl-3,5-dimethyl-2-pyrazoline-1-dithiocarboxylate (1) or benzyl 5-ferrocenyl-3,5-dimethyl-2-pyrazoline-1-dithiocarboxylate (2). The single crystals of both products are obtained and their structures are identified by X-ray diffraction method with triclinic P-1 space groups. The cell parameters for compound 1 are as follows: a = 7.7029(8) Å, b = 10.1631(11) Å, c = 10.7305(12) Å, α = 101.3270(10)°, β = 90.6740(10)°, γ = 94.8390(10)°, and V = 820.40(15) ų. For compound 2, the crystallographic data are: a = 7.953(3) Å, b = 10.970(5) Å, c = 12.534(3) Å, α = 84.718(5)°, β = 81.651(3)°, γ = 76.274(4)Å, and V = 1049.1(7) ų.     

Highly Polar Triterpenoid Saponins from the Roots of Saponaria officinalis L.

Five new triterpenoid saponins, including 3‐O‐β‐d ‐galactopyranosyl‐(1→2)‐[β‐d ‐xylopyranosyl‐(1→3)]‐β‐d ‐glucuronopyranosyl quillaic acid 28‐O‐β‐d ‐glucopyranosyl‐(1→3)‐β‐d ‐xylopyranosyl‐(1→4)‐α‐l ‐rhamnopyranosyl‐(1→2)‐[β‐d ‐xylopyranosyl‐(1→3)‐(4‐O‐acetyl)‐β‐d ‐quinovopyranosyl‐(1→4)]‐β‐d ‐fucopyranoside ( 1 ), 3‐O‐β‐d ‐galactopyranosyl‐(1→2)‐[β‐d ‐xylopyranosyl‐(1→3)]‐β‐d ‐glucuronopyranosyl quillaic acid 28‐O‐(6‐O‐acetyl)‐β‐d ‐glucopyranosyl‐(1→3)‐[β‐d ‐xylopyranosyl‐(1→4)]‐α‐l ‐rhamnopyranosyl‐(1→2)‐[β‐d ‐xylopyranosyl‐(1→3)‐(4‐O‐acetyl)‐β‐d ‐quinovopyranosyl‐(1→4)]‐β‐d ‐fucopyranoside ( 2 ), 3‐O‐β‐d ‐galactopyranosyl‐(1→2)‐[β‐d ‐xylopyranosyl‐(1→3)]‐β‐d ‐glucuronopyranosyl quillaic acid 28‐O‐β‐d ‐xylopyranosyl‐(1→4)‐α‐l ‐rhamnopyranosyl‐(1→2)‐[β‐d ‐xylopyranosyl‐(1→3)‐(4‐O‐acetyl)‐β‐d ‐quinovopyranosyl‐(1→4)]‐β‐d ‐fucopyranoside ( 3 ), 3‐O‐β‐d ‐galactopyranosyl‐(1→2)‐[β‐d ‐xylopyranosyl‐(1→3)]‐β‐d ‐glucuronopyranosyl quillaic acid 28‐O‐β‐d ‐glucopyranosyl‐(1→3)‐β‐d ‐xylopyranosyl‐(1→4)‐α‐l ‐rhamnopyranosyl‐(1→2)‐[(4‐O‐acetyl)‐β‐d ‐quinovopyranosyl‐(1→4)]‐β‐d ‐fucopyranoside ( 4 ), 3‐O‐β‐d ‐galactopyranosyl‐(1→2)‐[β‐d ‐xylopyranosyl‐(1→3)]‐β‐d ‐glucuronopyranosyl quillaic acid 28‐O‐(6‐O‐acetyl)‐β‐d ‐glucopyranosyl‐(1→3)‐[β‐d ‐xylopyranosyl‐(1→4)]‐α‐l ‐rhamnopyranosyl‐(1→2)‐[(4‐O‐acetyl)‐β‐d ‐quinovopyranosyl‐(1→4)]‐β‐d ‐fucopyranoside ( 5 ) together with two known congeners, saponariosides A ( 6 ) and B ( 7 ) were isolated from the roots of Saponaria officinalis L. Their structures were elucidated by extensive spectroscopic methods, including 1D‐ (¹H, ¹³C) and 2D‐NMR (DQF‐COSY, TOCSY, HSQC, and HMBC) experiments, HR‐ESI‐MS, and acid hydrolysis.     

A study of the structure and properties of mixed-ligand Cu(II) complexes with hexafluoroacetylacetone and methyl-, phenyl-ketoimines

The synthesis and X-ray single crystal study of two mixed-ligand Cu(II) complexes are performed: (CH₃C(NCH₃)CHC(O)CH₃)(CF₃C(O)CHC(O)CF₃)Cu (1) (space group P2₁/c, a = 7.0848(12) Å, b = 17.854(3) Å, c = 11.837(2) Å, β = 100.495(6)°, V = 1472.4(4) ų, Z = 4), (CH₃C(NC₆H₅)CHC(O)CH₃)· (CF₃C(O)CHC(O)CF₃)Cu (2) (space group P-1, a = 9.1119(4) Å, b = 9.6954(4) Å, c = 11.1447(6) Å, α = 113.784(2)°, β = 92.383(2)°, γ = 95.402(2)°, V = 893.52(7) ų, Z = 2). The structures are molecular, formed from neutral mixed-ligand copper complexes. The central copper atom has the (3O+N) coordination environment with average Cu-O distances of 1.948 Å and Cu-N of 1.932 Å; the chelate O-Cu-N angle (average) is 94.0°. In the structures, the complexes are linked into dimeric associates with Cu…Cu distances of 3.197 Å (for 1) and 3.246 Å (for 2). The volatility of mixed-ligand complexes 1 and 2 is in between of that of the starting homo-ligand complexes.     

Oligosaccharides Related to Tumor-Associate Antigens. Part 2. Conformational analysis of the trisaccharide α-L-Fucp-(1→2)-β-D-Galp-(1→3)-β-D-GalpNAc,epitope structure recognized by the MBr1 antibody

The conformational space of the trisaccharide α-L -Fuc-(1→2)-β- D -Gal-(1→3)-β -D -GalNAc-1-OPr ( 2 ) and of its component disaccharide moieties α -L -Fuc-(1→2)-β -D -Gal-1-OMe ( 3 ) and β -D -Gal-(1→3)-β- D -GalNAc-1-OPr ( 4 ) was investigated with the aid of molecular-mechanics energy minimizations and molecular-dynamics simulations. These calculations suggested the occurrence of two conformations for each compound characterized by different ? and Ψ glycosidic angles. However, ¹H-NMR investigation of D₂O solutions of 2–4 indicated a sure preference for one of the two conformers with a contribution of the other one ranging from negligible to low.     

The synthesis and crystal structure of 5-acetyl-2'-deoxyuridine

5- Acetyl - 2' - deoxyuridine (1) has been synthesised by treating 2' - deoxy - 5 - ethynyluridine with dilute sulphuric acid. Condensation of the trimethylsilyl derivative of 5-acetyluracil with 2-deox-3, 5-di-O-p-toluoyl-α-d-erythropen chloride gave a mixture of α- and β-anomeric blocked nucleosides from which the α-anomer was isolated and the p-toluoyl groups removed to give 5 - acetyl -1 - (α - d - 2- deoxyerythropentofuranosyl) uracil. Only a poor yield of the β-anomer (1) was obtained by this procedure. The UV spectra and m.p. obtained for 1 differed from the values quoted in the literature. The crystals of 1 are monoclinic, space group P2₁, with a = 9.525, b = 12.16, c = 5.22 Å, β = 92.03° and two molecules in the unit cell. The structure was refined by least-squares calculations to R 3.4% for 1426 observed counter amplitudes. The pyrimidine ring is essentially planar with the acetyl group inclined at 6° to it. The sugar ring has the highly unusual C(4')-exo conformation and the arrangement about C(4')-C(5') is such that O(5') is oriented gauche with respect to both O(1') and C(3'). The glycosidic torsion angle O(1')-C(1')-N(1)-C(6) is 56° (anti conformation).     

Convergent synthesis of a common pentasaccharide-repeating unit corresponding to the O-specific polysaccharide of Escherichia coli O4:K3, O4:K6, and O4:K12

A convergent chemical synthesis of a pentasaccharide found in the O-specific polysaccharide of Escherichia coli O4:K3, O4:K6, and O4:K12 has been achieved in excellent yield. A [3+2] block synthetic strategy has been adopted to couple a disaccharide donor 11 with a trisaccharide acceptor 10 for the construction of the pentasaccharide derivative 12 which on deprotection furnished target pentasaccharide 1 as its 4-methoxyphenyl glycoside. Disaccharide thioglycoside donor 11 and trisaccharide acceptor 10 were prepared from suitably protected monosaccharide intermediates. Yields were excellent in all steps.     

Electrical conductivity and phase transitions of the solid electrolyte system (Cs1−yRby)Cu4Cl3(I2−xClx)

Results of electrical conductivity measurements, thermal analysis, and X-ray diffraction studies indicate the existence of four phases, between 295 K and the melting points, in the system (Cs_1?yRb_y)Cu₄Cl₃I₂. These phases are designated α, á β, γ in order of decreasing temperature. The α phase is isostructural with α-RbAg₄I₅; the á phase is also cubic and very likely belongs to space groupP2₁3, a subgroup ofP4₁32 andP4₃32 to which the α phase belongs. There is a high probability that the á → α transition is continuous. The á → α transition is not discernible in the conductivity measurements or thermal analysis; therefore the line of á-α transitions is presently unknown. The β phase transforms to the á and the γ phase transforms to the β phase wheny ≤ 0.36; the γ phase transforms to the α phase wheny ≥ 0.36. That is, there is a triple point aty = 0.36, T = 399K. The γ-β, β-α′, and γ-α transitions are all hysteretic and are therefore first order. The conductivities of the β phases are relatively low and the enthalpies of activation relatively high. The conductivity of the β phase decreases with increasingy. The β phase probably belongs to space groupR3, in which the Cu⁺ ions can be ordered. The α and á phases are the true solid electrolytes; the conductivities are high, >0.73 Ω^?1cm^?1 at 419 K, and the enthalpies of activation of motion of the Cu⁺ ions low, 0.11 eV.In the system CsCu₄Cl₃(I_2?xCl_x), 0 ≤ x ≤ 0.25, the Cl^? for I^? substitutions affect the transitions to only a small extent relative to the stoichiometric compound. The β phase occurs for allx and transforms to á.     

Total Synthesis of 4′′‐O‐Acetylmananthoside B Part II: Synthesis of the Disaccharide Fragment

A disaccharide compound, p‐methoxyphenyl 2,3,4‐tri‐O‐benzyl‐β‐L‐arabinopyranosyl‐(1→6)‐2‐O‐benzyl‐3,4‐di‐O‐acetyl‐β‐D‐galactopyranoside ( 17 ), was successfully synthesized from two monosaccharides L‐arabinose and D‐galactose and fully characterized. This compound can be used to build a natural product 4″‐O‐acetylmanan thoside B, which was isolated from the leaves and stems of a kind of Vietnamese Acanthaceae Justicia patentiflora.     

Spectral and thermal properties,and the crystal structure of 1,4,5,8-naphthalene-tetracarboxylate dinuclear Ni(II) complex

A novel dinuclear Ni^II complex, [Ni₂(ntc)(H₂O)₁₀]·7(H₂O) (1), with 1,4,5,8-naphthaenetetracarboxylate (ntc) has been synthesized and characterized by X-ray diffraction analysis, IR, UV-vis spectra and thermogravimetric analysis. Complex 1 crystallizes in triclinic system, space group P-1, a = 7.721(3) Å, b = 9.458(3) Å, c = 11.453(4) Å, α = 114.110(6)°, β = 92.184(6)°, γ = 107.472(6)°, V = 715.7(4) ų, Z = 1, final R = 0.048. Each nickel atom is octahedrally coordinated by five aqua ligands and one oxygen atom of the bridging ntc connecting two nickel atoms. The resulting dinuclear Ni^II complex forms a 3D H-bonded network.     

Glycosidase-catalysed synthesis of mannobioses by the reverse hydrolysis activity of α-mannosidase: partial purification of α-mannosidases from almond meal,limpets and Aspergillus niger

Two disaccharides, α-d-Manp-(1→2)-d-Manp 6 and α-d-Manp-(1→3)-d-Manp 7, were synthesised from mannose using the reverse hydrolysis activity of the partially purified α-mannosidases from almond (Prunus amygdalus) meal and limpets (Patella vulgata). Both disaccharides were isolated by carbon–Celite chromatography. Attempts were also made towards the synthesis of core pentasaccharide using the purified α-mannosidase from Aspergillus niger.