Assignment Of Anomeric Configuration Research Articles

Krasilnikolides A and B and Detalosylkrasilnikolide A, Cytotoxic 20-Membered Macrolides from the Genus Krasilnikovia: Assignment of Anomeric Configuration by J-Based Configuration Analysis.

A chemical investigation of strain RD003821, belonging to the underexplored actinomycetes genus Krasilnikovia, led to the discovery of three novel polyketides: two 20-membered glycomacrolides, krasilnikolides A (1) and B (2), and an aglycone of 1, detalosylkrasilnikolide A (3). A major challenge in the structure elucidation of 1 was to determine the anomeric configuration of the α-l-6-deoxytalose (6dTal) unit, which was achieved by J-based configuration analysis (JBCA) that incorporated anomeric carbon- and proton-specific two-bond 13C-1H spin-spin coupling constants as diagnostic parameters. The updated criteria for the conformation/configuration assignment facilitated discrimination of three out of four stereochemical variants at the anomeric and the adjacent C2 positions, which expanded the scope of the JBCA method to determination of the anomeric configuration of aldohexopyranoses. Compounds 1 and 2 are the first macrolides decorated by 6dTal. Compounds 1-3 exhibited cytotoxicity against P388 murine leukemia cells with IC50 values of 14, 8.4, and 3.9 μM, respectively. In addition, 1-3 were antibacterial against the Gram-positive bacterium Kocuria rhizophila with MIC values of 25, 50, and 100 μg/mL. 1 was inhibitory against Staphylococcus aureus with an MIC of 50 μg/mL.

Selective formation of glycosidic linkages of N-unsubstituted 4-hydroxyquinolin-2-(1 H)-ones

A comparative study for selective glucosylation of N-unsubstituted 4-hydroxyquinolin-2(1 H)-ones into 4-(tetra- O-acetyl-β- d-glucopyranosyloxy)quinolin-2(1 H)-ones is reported. Four glycosyl donors including tetra- O-acetyl-α- d-glucopyranosyl bromide, β- d-glucose pentaacetate, glucose tetraacetate and tetra- O-acetyl-α- d-glucopyranosyl trichloroacetimidate were tested, along with different promoters and reaction conditions. The best results were obtained with tetra- O-acetyl-α- d-glucopyranosyl bromide with Cs 2CO 3 in CH 3CN. In some cases the 4-O-glucosylation of the quinolinone ring was accompanied by 2-O-glucosylation yielding the corresponding 2,4-bis(tetra- O-acetyl-β- d-glucopyranosyloxy)quinoline. Next, 4-(tetra- O-acetyl-β- d-glucopyranosyloxy)quinolin-2(1 H)-ones were deacetylated into 4-(β- d-glucopyranosyloxy)quinolin-2(1 H)-ones with Et 3N in MeOH. In some instances the deacetylation was accompanied by the sugar–aglycone bond cleavage. Structure elucidation, complete assignment of proton and carbon resonances as well as assignment of anomeric configuration for all the products under investigation were performed by 1D and 2D NMR spectroscopy.

Sequence determination of a non-sulfated glycosaminoglycan-like polysaccharide from melanin-free ink of the squid Ommastrephes bartrami by negative-ion electrospray tandem mass spectrometry and NMR spectroscopy

A non-sulfated polysaccharide was isolated from the ink sac of squid Ommastrephes bartrami after removal of the melanin granules. The carbohydrate sequence of this polysaccharide was assigned by negative-ion electrospray tandem mass spectrometry with collision-induced dissociation of the oligosaccharide fractions produced by partial acid hydrolysis of the polysaccharide. The structural determination was completed by NMR for assignment of anomeric configuration and confirmation of linkage information and it was unambiguously identified as a glycosaminoglycan-like polysaccharide containing a glucuronic acid-fucose (GlcA-Fuc) disaccharide repeat in the main chain and a N-acetylgalactosamine (GalNAc) branch at Fuc position 3: -[3GlcAbeta1-4(GalNAcalpha1-3)Fucalpha1](n)-. Partial hydrolysis of the polysaccharide to obtain several oligosaccharide fractions with different numbers of the repeating unit assisted the assignment. In the negative-ion tandem mass spectrometric analysis, the unique (0,2)A type fragmentation was important to establish the presence of a 4-linked fucose in the main polysaccharide chain and a GalNAc branch at the Fuc position-3 of the disaccharide repeat.

ChemInform Abstract: Assignment of Anomeric Configuration

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On the Assignment of Anomeric Configuration

AbstractOne of the diversities of carbohydrate structure lies in their ability to form different anomers from the monosaccharide unit. Unfortunately, the question of assignment of anomers has not been dealt with properly or accurately in most organic and biochemical textbooks and reference books. In this article, the question of assignment of anomers is examined from several different standpoints and an easy solution for this tricky problem is suggested.

Assignment of anomeric configuration of C-glycopyranosides and C-glycofuranosides. A proton, carbon-13, and nuclear Overhauser enhancement spectrometric study

The utility of 1 H, 13 C, and nuclear Overhauser enhancement spectrometries for assignment of C-glycopyranosides and C-glycofuranosides to α or β another series has been assessed. Specifically examined were 1 H- 1 H coupling constants J 1',2' and J 4',5' , 1 H chemical shifts δ H1' , 13 C chemical shifts δ C1' and δ C5' , 1 H- 13 C coupling constants J C1',H1' , and nuclear Overhauser effects (NOE) observed upon irradiation of H1', H4', and H5'. While all of these data have been used for assignment of anomeric configuration of C-glycosides, this study demonstrates that the NOE obtained by irradiation of H1' is uniquely reliable

Assignment of Anomeric Configuration of D-Ribo-, Arabino-, 2′-Deoxyribo-, and 2′,3′-Dideoxyribonucleosides by Noe Difference Spectroscopy

Abstract The anomeric configuration of D-ribo-, D-arabi-no, D-2′-deoxyribo-, and D-2′,3′-dideoxyribonucleosides was assigned unambiguously applying n.O.e. difference spectros-copy. For this purpose 1′-H, signals were saturated and the n.O.e. factors of 4′-H, 3′-H, and 2′-H were measured.

Unambiguous Assignment of Anomeric Configuration of Nucleosides by Noe-Difference Spectroscopy

Abstract An unambiguous assignment of anomeric configuration of D-ribo-, 2′-deoxy-D-ribo-, D-arabino and 2′,3′-dideoxy-D-ribonucleosides based on nuclear Overhauser enhancement spectroscopy is presented.

Assignment of Anomeric Configuration and Identification of Carbohydrate Residues by13C NMR: Arabino- and Ribopyranosides and Furancsides

Abstract A 13C NMR fingerprint method previously developed for galactosides and glucosides is extended to arabinosides and ribosides. This approach demonstrates the capability of 13C NMR to determine ring size and anomeric configuration in four isomeric arabinosides and ribosides.

Assignment of anomeric configuration and identification of carbohydrate residues by 13C nmr. 1. Galacto- and glucopyranosides and furanosides

A 13C nmr analysis method is described for the identification of carbohydrate residues in galactosides and glucosides. This method reveals the capability of 13C nmr to distinguish the difference in structural configuration of these carbohydrate residues. Not only can the anomeric configuration be assigned, the furanyl and pyranyl nature of the ring is concomitantly determined. This method is consistent for all reported 13C nmr spectra of nonaromatic galactosides and glucosides.

Phosphorus-31 nuclear magnetic resonance spectroscopy of extracellular, yeast O-phosphono-hexoglycans

31P nuclear magnetic resonance spectra of a number of purified yeast O-phosphonohexoglycans were recorded. The data therefrom were correlated with established chemical aspects of individual and collective polymer structures, permitting ( a) conclusions to be drawn regarding the chemical environment of the phosphate groups of these polymers, and ( b) assignment of anomeric configuration to the hexosyl phosphate residues.

Synthesis and properties of 2,3-anhydro-D-mannose and 3,4-anhydro-D-altrose

Treatment of benzyl 3,4,6-tri-O-acetyl-2-O-p-tolylsulphonyl-β-D-glucopyranoside (5) with sodium methoxide in methanol gave benzyl 2,3-anhydro-β-D-mannopyranoside (7)(65%) and benzyl 3,4-anhydro-β-D-altropyranoside (8)(29%). Hydrogenolysis of the glycoside (7) in tetrahydrofuran over palladium–charcoal yielded crystalline 2,3-anhydro-β-D-mannopyranose (9) which, in aqueous solution, rapidly underwent mutarotation to give an equilibrium mixture containing the α-pyranose (10)(23%), the β-pyranose (9)(7%), the α-furanose (12)(65%), and the β-furanose (11)(5%), whose composition was determined by g.l.c., g.l.c.–mass spectrometry, and n.m.r. spectroscopy; the assignment of anomeric configuration to the furanose isomers rests on conformational arguments. A similar mixture was obtained by hydrogenolysis of benzyl 2,3-anhydro-α-D-mannopyranoside (13). Hydrogenolysis of the glycoside (8) in methanol gave an equilibrium mixture of the α- and β-forms [(14) and (15)] of 3,4-anhydro-D-altropyranose (32.5 and 67.5%, respectively).

Deazapurine derivatives. IX: Synthesis of (7‐substituted)‐1‐, 2‐ and 3‐β‐D‐ribofuranosyl‐vic‐triazolo [4,5‐b]pyridines. 1‐Deaza‐8‐aza‐adenosine and related compounds

AbstractThe direct condensation of 7‐chloro‐vic‐triazolo[4,5‐b]pyridine (I) with 2,3,5‐tri‐O‐benzoylribofuranosyl chloride (III) in nitromethane containing potassium cyanide, afforded two isomeric blocked nucleosides. Debenzoylation of these products gave the ribosides 7‐chloro‐3‐β‐D‐ribofuranosyl‐vic‐triazolo[4,5‐b]‐pyridine (VI) and its 2‐ribosylated isomer VII. From the reaction of the chloromercuri derivative of vic‐triazolo[4.5‐b]pyridine (X) with III in boiling toluene, followed by subsequent debenzoylation of the reaction products, three isomeric ribosides were obtained: 1‐, 2‐ and 3‐β‐D‐ribofuranosyl‐vic‐triazolo[4,5‐b]‐pyridine (XVI, XV and XIV). The position of attachment of the sugar moiety to the vic‐triazolo[4.5‐b]pyridine ring system and the assignment of anomeric configuration for all nucleosides reported, are discussed. A number of 7‐substituted 3‐β‐D‐ribofuranosyl‐vic‐triazolo[4,5‐b]pyridines ‐ including 1‐deaza‐8‐aza‐adenosine (XXVI) ‐ was obtained by replacement of the chloro group of VI.

The synthesis and PMR study of certain 3‐substituted 2‐(β‐D‐Ribofuranosyl)indazoles

AbstractThe synthesis of 3‐cyano‐2‐(β‐D‐ribofuranosyl)indazole (4) has been accomplished by a condensation of N‐trimethylsilyl‐3‐cyanoindazole (1) with 2,3,5‐tri‐O‐aeetyl‐D‐ribofuranosyl bromide (2) followed by subsequent deacetylation. The reactivity of the 3‐cyano group was demonstrated by the conversion of 4 to 2‐(β‐D‐ribofuranosyl)indazole‐3‐carboxamide (5) and 2‐(β‐D‐ribofuranosyl)indazole‐3‐thiocarboxamide (6). The site of ribosylation and the assignment of anomeric configuration for 4 is discussed. The magnetic anisotropy effect of the exocyclic group at C3 on the anomeric proton as determined by pmr spectroscopy is discussed.

The synthesis of certain ribofuranosylindazoles

AbstractThe synthesis of 1‐(β‐D‐ribofuranosyl)indazole (4), 2‐(β‐D‐ribofuranosyl)indazole (5) and 6‐, 5‐, and 4‐nitro‐2‐(β‐D‐ribofuranosyl)indazole (8a, 8b, and 8c, respectively), has been accomplished in good yield by the condensation of the appropriate N‐trimethylsilylindazole (1, 6a, 6b, and 6c) with 2,3,5‐tri‐O‐acetyl‐D ‐ribofuranosyl bromide (2) followed by subsequent deacetylation of the reaction products. The site of ribosylation and the assignment of anomeric configuration for all nucleosides reported is discussed. This has furnished the first indazole nucleosides with assigned anomeric configurations and the site of ribosylation has been established on the basis of uv comparisons with model methyl compounds.

A convenient synthesis of certain 1‐(β‐D‐ribofuranosyl)benzotriazoles

AbstractThe synthesis of 5,6‐dichloro‐1‐(β‐D‐ribofuranosyl)benzotriazole (4a), 5,6‐dimethyl‐1‐(β‐D‐ribofuranosyl)benzotriazole (4b) and 1‐(β‐D‐ribofuranosyl)benzotriazole (4c) in good yield has been accomplished by the condensation of the appropriate 1‐trimethylsilylbenzotriazole (1a, 1b, and 1c) with 2,3,5‐tri‐O‐acetyl‐D‐ribofuranosyl bromide (2) followed by subsequent deacetylation of the reaction products. The assignment of anomeric configuration and site of glycosidation for all nucleosides reported is discussed.

The synthesis of 2‐chloro‐1‐β‐D‐ribofuranosyl‐5,6‐dimethylbenzimidazole and (certain related derivatives

AbstractThe synthesis of 2‐chloro‐1‐(β‐D‐ribofuranosyl)‐5,6‐dimethylbenzimidazole (3b) has been accomplished by a condensation of 1‐trimethylsilyl‐2‐chloro‐5,6‐dimethylbenzimidazole (1) with 2,3,5‐tri‐O‐acetyl‐D‐ribofuranosyl bromide (2) followed by subsequent deacetylation. Nucleophilic displacement of the 2‐chloro group from 3b has furnished several interesting 2‐substituted‐1‐(β‐D‐ribofuranosyl)‐5,6‐dimethylbenzimidazoles. 1‐(β‐D‐Ribofuranosyl)‐5,6‐dimethylbenzimidazole (5) and 1‐(β‐D‐ribofuranosyl)‐5,6‐dimethylbenzimidazole‐2‐thione (4) were prepared from 3b. Alkylation of 4 furnished certain 2‐alkylthio‐1‐(β‐D‐ribofuranosyl)‐5,6‐dirnethylbenzimidazoles and oxidation of 4 with alkaline hydrogen peroxide produced 1‐(β‐D‐ribofuranosyl)‐5,6‐dimethylbenzimidazole‐2‐one D The assignment of anomeric configuration for all nucleosides reported is discussed.

The synthesis of 2‐chloro‐1‐(β‐D‐ribofuranosyl)benzimidazole and certain related derivatives

AbstractThe synthesis of 2‐chloro‐1‐(β‐D‐ribofuranosyl)benzimidazole (4b) has been accomplished by a condensation of 2‐chloro‐1‐trimethylsilylbenzimidazole (1) with 2,3,5‐tri‐O‐acetyl‐D‐ribofuranosyl bromide (2) followed by subsequent deacetylation. Nucleophilic displacement of the 2‐chloro group has furnished several interesting 2‐substituted‐1‐(β‐D‐ribofuranosyl)benzimidazoles. 1‐(β‐D‐Ribofuranosyl)benzimidazole (5) and 1‐(β‐D‐ribofuranosyl)benzimidazole‐2‐thione (6) were prepared from 4b and 6 was also prepared by condensation of 2 with silylated benzimidazole‐ 2‐thione (3). Alkylation of 6 furnished certain 2‐alkylthio‐1‐(β‐D‐ribofuranosyl)benzimidazoles and oxidation of 6 with alkaline hydrogen peroxide produced 1‐(β‐D‐ribofuranosyl)benzimidazole‐2‐one (9). The assignment of anomeric configuration for all nucleosides reported is discussed.

Pyrrolopyrimidine nucleosides II. the total synthesis of 7‐β‐D‐ribofuranosylpyrrolo[2,3‐d]pyrimidines related to toyocamycin

AbstractThe first synthesis of a 7‐β‐D‐ribofuranosylpyrrolo[2,3‐d]pyrimidine by direct ribosidation of a preformed pyrrolo[2,3‐d]pyrimidine has now been accomplished via the fusion procedure. Subsequent functional group transformations furnished the 6‐methyl‐thio derivative of the nucleoside antibiotic toyocamycin. Preparation of the 1‐, 3‐ and 7‐methyl isomers of 4‐amino‐5‐cyano‐6‐methylthiopyrrolo[2,3‐d]pyrimidine was accomplished and has provided an unequivocal assignment for the actual site of ribosidation by a comparison of ultraviolet absorption spectra. Factors utilized for the assignment of anomeric configuration are discussed.