Synthesis of a (1→6)-β-Linked N-Acetyl-d-glucosamine Oligosaccharide1

Abstract

1,6-Anhydro-2-deoxy-3,4-di-O-benzyl-2-phthalimido-β-d- glucopyranose (5) was synthesized from 1,6-anhydro-β-d-mannopyranose (1) in five steps. Compound 5 was polymerized under cationic conditions and selectively yielded glucosamine oligomers (degree of polymerization 5-7). Copolymerization of 5 with 1,6-anhydro-2,3,4-tri-O-benzyl-β-d-glucopyranose indicated the low reactivity of 5 with the active cation derived from 5. Deprotection of 2-deoxy-3,4-di-O-benzyl-2-phthalimido-(1→6)-β-d-glucopyranan (7) and N-acetylation gave 2-acetamido-2-deoxy-(1→6)-β-d-glucopyranan (9).     

Synthesis of Novel Bis(mesocyclic) polyamines

介绍了带羟基桥连双－（中环多胺）的合成。首先利用Ｎ－对甲苯磺酰基－３－羟基－１，５－二氮杂环庚烷与５种双官能基化合物在Ｎ２气氛下于无水乙腈中反应，得到５种带对甲苯磺酰基的中环多胺，然后利用ＨＢｒ／ＨＯＡｃ脱去保护基团，得到桥连双－（中环多胺）的氢溴酸盐。所有新化合物的结构均经ＩＲ、１ＨＮＭＲ、ＭＳ或元素分析证实。     

Synthesis of Methyl O-β-D-Ouactopyrmosyl-(1+6)-(3-Deoxy-3-Fluoro-β-D-Galactopyranosyl)-(1→6)-β-D-Galactopyranoside. Confirmation of the Location of Subsite D in the Monoclonal IgA J539

Bromoacetylation of methyl 2,4-di-O-benzoyl-3-deoxy-3-fluoro-β-D-galactopyranoside, followed by the cleavage of the methoxy group from the resulting 6-O-bromoacetyl derivative 2 with 1,1-dichloromethyl methyl ether gave 2,4-di-0-benzoyl-6-0-bromoacetyl-3-deoxy-3-fluoro-α-D-galactopyranosyl chloride (3). Reaction of 3 with methyl 2,3,4-tri-O-benzoyl-β-D-galactopyranoside promoted by silver trifluoromethanesulfonate afforded methyl 0-(2,4-di-O-benzoyl-6-O-bromoacetyl-3-deoxy-3-fluoro-β-D-galacto-pyranosyl)-(1→6)-2,3,4-tri-O-benzoyl-β-D-galactopyranoside (5). O-Debromoacetylation of 5 with thiourea gave the disaccharide nucleophile 6 which was condensed with 2,3,4,6-tetra-O-benzoyl-α-D-galactopyranosyl bromide to afford the expected β-(trans)-linked trisaccharide derivative 7. Debenzoylation of 7 gave the methyl β-glycoside 8 of the (1→6)-linked D-galactotriose having the HO-3 of the internal residue replaced by a fluorine atom. Compound 8 was used to further delineate the subsites in the combining area of the monoclonal anti-(1→6)-β-D-galactan-specific immunoglobulin IgA J539.     

Synthesis of Two Isomeric Tetrasaccharides 0-α-L-Fucopyranosyl-(1→3) and (1→4)-0-(2-Acetamido-2-Deoxy-β-D-Glucopyranosyl)-(1→3)-0-(β-D-Galactopyranosyl)-(1→4)-D-Glucopyranose and a Related Tetrasaccharide 0-α-L-Fucopyranosyl-(1→3)-0-(2-Acetamido-2-Deoxy-β-D-Glucopyranosyl-(1→6)-0-(β-D-Galactopyranosyl)-(1→4)-D-Glucopyranose

ABSTRACT

Synthesis of three tetrasaccharides, namely, 0-α-L-fucopyranosyl-(1→3)-0-(2-acetamido-2-deoxy-β-D-glucopyranosyl)-(1→3)-0-(β-D-galactopyranosyl)-(1→4)-β-D-glucopyranose (7), 0-α-L-fucopyranosyl-(1→4)-0-(2-acetamido-2-deoxy-β-D-glucopyranosyl)-(1→3)-0-(β-D-galactopyranosyl)-(1→4)-D-glucopyranose (9), and 0-α-L-fucopyransoyl-(1→3)-0-(2-acetamido-2-deoxy-β-D-glucopyransoyl)-(1→6)-0-(β-D-galactopyranosyl)-(1→4)-D-glucopyranose (15) has been described. Their structures have been established by ¹³C NMR spectroscopy.     

Synthesis and Electrochemical Studies of Ruthenium(II) Dicarbonyl Bis(ferrocenyl-β-diketonates)

The reaction of [Ru₃(CO)₁₂] ( 1 ) with six equiv. of FcC(O)CH₂C(O)R ( 2a , R = Me; 2b , R = Fc; Fc = Fe(η⁵-C₅H₄)(η⁵-C₅H₅)) produced the Ru^II compounds [Ru(CO)₂(FcC(O)CHC(O)R)₂] ( 3a , R = Me; 3b , R = Fc) in moderate yields. IR studies and single-crystal X-ray analysis ( 3a ) confirmed that the CO ligands are cis-oriented and that the respective β-diketonates O,O'-chelate-bonded setting-up an octahedral surrounding at Ru^II. Electrochemical (cyclic and square-wave voltammetry) and spectroelectrochemical (UV/Vis-NIR, IR) measurements were additionally carried out. Compounds 3a , b display two ( 3a : E₁^o' = 140; E₂^o' = 255 mV; ΔE^o' = 115 mV for [ 3a ]⁺/[ 3a ]²⁺) or four ( 3b : E₁^o' = 80 mV, E₂^o' 190 mV (ΔE^o' = 110 mV, [ 3b ]⁺/[ 3b ]²⁺), E₃^o' = 355 mV (ΔE^o' = 165 mV, [ 3b ]²⁺/[ 3b ]³⁺), E₄^o' = 490 mV (ΔE^o' = 135 mV, [ 3b ]³⁺/[ 3b ]⁴⁺)) electrochemical reversible one-electron redox processes indicating electrostatic interactions among the ferrocenyl groups as oxidation progresses, which was confirmed by UV/Vis-NIR and in situ IR spectroscopy. One ferrocenyl group on each β-diketonate ligand is by this means 1^st oxidized before the 2^nd ferrocenyl group of the same β-diketonate building block follows.     

Iodonium-Ion Assisted Stereospecific Glycosylation: Synthesis of Oligosaccharides Containing α(1-4)-Linked L-Fucopyranosyl Units

ABSTRACT

The terminal glycosyl acceptor methyl 2,3-di-O-benzyl-α-L-fucopyranoside (6) was extended three times with the non-terminal glycosyl donor ethyl 4-O-acetyl-2,3-di-O-benzyl-1-thio-ß-L-fucopyranoside (13) via iodonium-ion assisted glycosylations and intermittent removal of the C-4 acetyl group in intermediate dimer 16 and trimer 18. The 4-O-acetyl group in trimer 18 and tetramer 20 was highly resistant towards basic hydrolysis. The latter could be nullified by using dichloroacetyl instead of acetyl to protect the C-4-OH in the donor. The exclusive formation of 1,2-cis-linked oligomers could be explained by through-bond interactions exerted by the electron-withdrawing C-4 acyl group in the glycosyl donor.     

Synthesis of p-Trifluoroacetamidophenylethyl O-(2-Acetamido-2-Deoxy-β-D-Galactopyranosyl)-(1→4)-O-β-D- Galactopyanosyl-(1→4)-O-β-D-Glucopyranoside,Containing the Trisaccharide Portion of the Asialo-GM2 Glycolipid

ABSTRACT

The p-trifluoroacetamidophenylethyl β-glycoside 9 of the trisaccharide O-(2-acetamido-2-deoxy-β-D-galactopyranosyl)-(1→4)-O-β-D-galactopyranosyl-(1→4)-D-glucopyranose (gangliotriose, asialo-GM2) was synthesised. The key step was coupling of a suitably protected lactose derivative with a galactosamine thioglycoside derivative using sulfuryl chloride/trifluoromethanesulfonic acid activation.     

Total Synthesis of (R)-(−)-β-Cuparenone

Abstract

(R)-(?)-β-Cuparenone has been synthesized from (S)-(+)-acid-2 obtained via resolution of the racemic acid. Two of the noteworthy steps are (a) repeated methylation of ester (+)-8 with LDA/MeI to furnish (+)-10 and (b) the reaction of 12, having two neopentyl units with NaCN.     

Synthesis and Crystal Structure of Bis(S-methyl-β-N- (4-dimethylaminophenyl)methlenedithiocarbazate) Nickel (Ⅱ)

11NTRoDUCT1ONRecently,transitionmetalorganometallicandcoordinationcomplexeshavee-mergedaspotentialbuildingblocksfornonlinearoptical(NLO)materials(l-5i.Com-paredwlthorganlcmolecu1es,metalcomplexesofferalargervarietyofstructures,comparabIeor,insomecases,higherenvironmenta1stabilityandamuchgreaterdi-versityoftunableelectronicpropertiesbythevirtueofthecoordinatedmetalcen-tert6i.Thethio-Schiffbaseligandderivedfromdithiocarbazatesandthiosemicar-bazidescancoordinatereadilywithtransitionmetalstog…     

Synthesis of ( )-5α-Hydroxy-β-selinene and (-)-5β-Hydroxy-β-selinene

Eudesmanederivativeshavebeendrawingconsiderableattentionduetotheirwidespectrumofbiologicalproperties,particularlyantifeedant,cellgroWthinhibitoryandplantgroWthregulatingactivitiesl'2.Recently,twoepimericeudesmanederivatives( )-5a-hydroxy-6-selinene1and(-)-56-hydroxy-6-selinene2wereisolated3fromtheaerialpartsofCSubtraPicaFMell.,andtheirstructuresweredeterminedbyspectroscopicmethods.Herein,wereportafacilesynthesisofbothtwodiastereomers1and2from( )-dihydrocarvone3infivesteps,usingtheregioselect…     

Synthesis of stigmasteryl (β1→4)-oligoglucosides

Stigmasteryl (β1→4)-oligoglucosides were prepared with cellobiose, cellotriose, and cellotetraose as glycan chains. For the preparation of the peracetylated oligoglucosyl donors anomeric acetate was deprotected and the respective hemiacetals were converted into trichloroacetimidates. Glycosylation with stigmasterol yielded both α- and β-anomers because during the treatment with Lewis acid the 2-OAc is cleaved to some extent; thus, with the emerging hydroxyl group neighboring group participation does not take place. Due to their different number of hydroxyl groups (0 vs. 1) separation of the two products proved to be facile. Saponification led to the desired stigmasteryl glucosides.     

Stereoselective Synthesis of (Z)-β-Aryltellurocinnamic Esters

ＳｔｅｒｅｏｓｅｌｅｃｔｉｖｅＳｙｎｔｈｅｓｉｓｏｆ（Ｚ）－β－ＡｒｙｌｔｅｌｌｕｒｏｃｉｎｎａｍｉｃＥｓｔｅｒｓ￥ＣｈａｎｇＱｉｕＺＨＡＯ；ＸｉａｎＨＵＡＮＧ（ＤｅｐａｒｔｍｅｎｔｏｆＣｈｅｍｉｓｔｒｙ，ＨａｎｇｚｈｏｕＵｎｉｖｅｒｓｉｔｙ，Ｈａｎ...     

Synthesis and Thermal Rearrangement of Tetramethyldisilane-bridged Bis(cyclopentadienyl) Diiron Complexes with Bis(phosphine)Substitution

Photolysis of [Me2SiSiMe2)[C5H4Fe(CO2)]2with a series of bis(phosphine)ligands Ph2P(CH2)n PPh2(n=1-4) leads to the formation of the corresponding diiron complexes with intramolecular and intermolecular bis(phosphine) substitution.When these complexes were heated in refluxing xylene.only in the complexes with intermolecular bis(phosphine )substitution the thermal rearrangement reaction occurred.     

Synthesis and Crystal Structure of Tetraaquacopper(II) Bis(5-fluorouracil-1-acetate) Tetrahydrate

1 INTRODUCTION 5-Fluorouracil (5-FU) is an antimetabolite with good antimicrobial and antitumor activities but has toxic side effects[1~4]. In order to improve the topical delivery of 5-FU and reduce the side effects, many derivatives of 5-FU have been synthesized, some of which are of improved activity. 5-Fluorou- racil-1-acetic acid is a member of the family[5~8], which belongs to the pyrimidine base and is a cyto-toxic analogue of the natural base thymine, and has proven useful in th…     

Synthesis of Bis(macrocyclic) Polyamines Containing Rigid Bridging Groups

Thesgnthesi8ofbis(macrocyclic)POlyamineligandsandtheirdinuclearcomplexesoftransitionmetalionshaveattractedmuchinterestinrecentyears.Andava-rietyofsyStemshavebeenreported[1-s1.Theprotonatedfreeligandshavebeenusedashostsforanionicsubstrates.Theresultingdinuc1earcomplexeshavebeenstudiedasmodelsfortheactivesitesofphosphateases.Ofspecialinterestisthehydrolysisofactivatedphosphatemonoester[3J.Here,weconfineourreporttothesrothe8isofthreenew8ymmetricalbis(1,4,7-triazacyclononane)ligandsNa-ccontaini…     

Synthesis of Bis(Trifluoromethyl)-2,2′- Bipyridines by Nickel Catalysed Homocoupling Reactions

Bis(trifluoromethyl)-2,2′-bipyridines have been synthesized in moderate yields by nickel or palladium catalysed homocoupling of 2-chloro(trifluoromethyl) pyridines.     

Synthesis of 1-(1-aryl-1H-1,2,3-triazol-4-yl)-β-carboline derivatives

Reaction of 5-methyl-1-aryl-1H-1,2,3-triazole-4-carbocylic acid chlorides with tryptamine derivatives afforded substituted 1-aryl-N-[2-(1H-indol-3-yl)ethyl]-5-methyl-1H-1,2,3-triazole-4-carboxamides. At heating these compounds in toluene in the presence of POCl₃ and P₂O₅ Bischler-Napieralski cyclization occurs giving 1-(1-aryl-5-methyl-1H-1,2,3-triazol-4-yl)-4,9-dihydro-3H-β-carbolines that can be transformed into β-carboline and tetrahydro-β-carboline derivatives.     

Solid-Phase Total Synthesis of 1-β-Methylcarbapenem

A 1-β-methylcarbapenem analogue 6 was synthesized on polystyrene-diethylsilane resion (PS-DES) using 2-azetidinone bearing with 2-oxazolidone chiral auxiliary as starting material.     

Stereoselective Synthesis of Novel C-Disaccharides via Suzuki Cross-Coupling Reaction

Novel β-C-disaccharides containing a three carbon linkage using exo-glycal as the precursor were prepared stereoselectively. The synthesis was achieved by the tandem reactions of the stereoselective hydroboration of exo-glycal and Suzuki cross-coupling reaction with an iodovinyl sugar, and followed by hydrogenated deprotection under the catalysis of Pd（OH）2/C.