Anthony Serianni - Academia.edu (original) (raw)
Papers by Anthony Serianni
Carbohydrate Research, Jun 1, 1987
Chemical methods are described for preparing unenriched and [1-13C]-enriched 5-deoxy- and 5-O-met... more Chemical methods are described for preparing unenriched and [1-13C]-enriched 5-deoxy- and 5-O-methyl-pentoses in the D or L configuration. The 1H-n.m.r. spectra of these compounds have been interpreted, and the 13C-n.m.r. spectra assigned with the aid of 2-D 13C-1H chemical-shift correlation spectroscopy. Tautomeric forms (furanoses, hydrate, and aldehyde) in solution in 2H2O have been quantified with the aid of [1-13C]-enriched derivatives. Spectra of 5-deoxypentoses, 5-O-methylpentoses, and methyl pentofuranosides have been compared, in order to assess the effect of 5-C-deoxygenation and 5-O-methylation on chemical shifts and coupling constants (1H-1H, 13C-1H, and 13C-13C) and on the pentofuranose conformations.
Physical Chemistry Chemical Physics, 2023
The dependence of calculated 1JC1,C2 values on the C1–C2–O2–H torsion angles θ2 in several methyl... more The dependence of calculated 1JC1,C2 values on the C1–C2–O2–H torsion angles θ2 in several methyl aldohexopyranosides.
Accounts of Chemical Research, Aug 11, 2023
ChemInform, Jan 15, 2008
ABSTRACT
Magnetic Resonance in Chemistry, Feb 1, 1988
Adenosine, cytidine, guanosine and uridine were prepared with stereoselective deuteriation at C-5... more Adenosine, cytidine, guanosine and uridine were prepared with stereoselective deuteriation at C-5' and used to assign the prochiral C-5' protons in 300 MHz 'H NMR spectra. In all cases, the more shielded C-5' proton was found to be the pro-R proton. From these assignments, C-4'-C-5' rotamer populations have been estimated, and some discussion of the errors associated with these calculations is given. The relative populations of rotamers in ribonucleosides were found to be affected by structure at C-1, ring conformation and possibly solution pH.
Carbohydrate Research, Mar 1, 2020
Sugar 1,2-orthoesters are by-products of chemical glycosylation reactions that can be subsequentl... more Sugar 1,2-orthoesters are by-products of chemical glycosylation reactions that can be subsequently rearranged in situ to give trans glycosides. They have been used as donors in the synthesis of the latter glycosides with good regio- and stereo-selectivity. Alkyl α-(1 → 2) linked mannopyranosyl disaccharides have been reported as the major products from the rearrangement of mannopyranosyl orthoesters. Recent studies in this laboratory have shown that α-(1 → 2) linked mannopyranosyl di-, tri- and tetrasaccharides can be obtained in one step from mannopyranosyl allyl orthoester under optimized reaction conditions. In addition to the expected mono- and disaccharides (56%), allyl 2,3,4,6-tetra-O-acetyl-α-D-mannopyranosyl-(1 → 2)-3,4,6-tri-O-acetyl-α-D-mannopyranosyl-(1 → 2)-tri-O-acetyl-α-D-mannopyranoside and allyl 2,3,4,6-tetra-O-acetyl-α-D-mannopyranosyl-(1 → 2)-3,4,6-tri-O-acetyl-α-D-mannopyranosyl-(1 → 2)-3,4,6-tri-O-acetyl-α-D-mannopyranosyl-(1 → 2)-3,4,6-tri-Oacetyl-α-D-mannopyranoside were obtained in 23% and 6% isolated yields, respectively, from the oligomerization of a β-D-mannopyranosyl allyl 1,2-orthoester, along with small amounts of higher DP oligomers. Possible mechanisms for the oligomerization and side reactions are proposed based on NMR and mass spectrometric data.
Journal of Organic Chemistry, Mar 20, 2007
Reaction of a galactosylated 2-C-(hydroxymethyl)-tetrofuranose with paramolybdate ion-exchange re... more Reaction of a galactosylated 2-C-(hydroxymethyl)-tetrofuranose with paramolybdate ion-exchange resin in aqueous solution at 67°C gave an equililibrium mixture containing the reactant aldofuranose (42%) and a 2-ketopentofuranose galactosylated at O1 (58%). Observation of this stereospecific rearrangement supports prior arguments that substituents at C2 of the branched-chain aldofuranose reactant are located in a sterically accessible pocket of the putative dimolybdatesaccharide reactive complex during epimerization. This rearrangement provides a new and convenient route to 2-ketosugars glycosylated at the exocyclic C1 position. Carbohydrate complexes with cations and anions in aqueous solution have been studied extensively by Angyal and others 1,2 and form the basis of convenient chromatographic methods to separate and purify saccharides. 3-5 Ion binding strength is determined partly by the relative configuration of hydroxyl ligands on the saccharide. For example, complexation of the divalent Ca 2+ ion is strongest for aldopyranosyl rings containing contiguous ax-eq-ax arrangements, whereas the presence of cis-1,2-OH groups is important for cation binding to aldofuranosyl rings. Cation binding to sugars is relatively weak, however, and the biological implications of these interactions remain unclear. Anions such as borate, tungstate, arsenate, and molybdate bind saccharides strongly, but interestingly, the former three produce stable, unreactive complexes, whereas the latter forms a highly reactive complex that promotes an unusual, stereospecific rearrangement of the carbon skeleton. 6 For example, the addition of catalytic amounts of resin-bound molybdate 7 to an aqueous solution of D-[1-13 C]erythrose 1 (pH 4.2) at 90°C yields an equilibrium mixture of 1 (∼35%) and D-[2-13 C]threose 2 (∼65%) after ∼3 h (Scheme 1). C2-Epimerization occurs with C1-C2 transposition and appears to proceed via an acyclic dimolybdate-saccharide intermediate. 6 Recent work has shown that the aldehydic proton of 1 can be replaced by CH 2 OH, CH 3 , or CH 2 OPh substituents without compromising the viability of the transformation. 8 2-C-(Methyl)-D-erythrose 3 and 1-deoxy-D-xylulose 4 are thus interconverted by molybdate anion in aqueous solution, with the latter highly favored at equilibrium (Scheme 1). Given the tolerance for simple functional groups at C2 of branched-chain aldotetroses, we examined whether the rearrangement would proceed with a glycosyl residue present at this position. Methyl 2-C-(hydroxymethyl)-2,3-O-isopropylidene-D-erythrofuranoside 5 8 was prepared and condensed with 2,3,4,6-tetra-O-acetyl-R-D-galactopyranosyl bromide 6. Deprotection afforded-D-galactopyranosyl-(1f2C)-2-C-(hydroxymethyl)-D-erythrose (7) (Scheme 2). The 1 H NMR spectrum of 7 (Figure S1, Supporting Information) contained two singlets at 5.234 and 5.243 ppm, which were assigned to the furanose anomeric protons H1 (Table 1). Signal integration gave a 42/58 ratio, with the downfield H1 signal more intense. Two additional anomeric 1 H signals at 4.436 and 4.403 ppm appeared as doublets with 3 J H1′,H2′) 7.8 Hz. These signals were assigned to H1′ of the Gal residue. The relatively large 3 J H1′,H2′ values show that the linkage has the-configuration. Anomeric carbon signals were observed at 106.31, 105.95, 104.16, and 99.98 ppm (Figure S2, Table 1). The former two correlated with the Gal H1′ signals, and the latter two with the anomeric furanose signals (i.e., 104.16/5.234 and 99.98/5.243
Journal of Organic Chemistry, Jun 1, 2000
The reaction of D-mannose and D-allose with [PtMe 3 (Me 2 CO) 3 ]BF 4 1 in acetone affords comple... more The reaction of D-mannose and D-allose with [PtMe 3 (Me 2 CO) 3 ]BF 4 1 in acetone affords complexes [PtMe 3 L]BF 4 5 and 6 (5, L) R-D-mannofuranose; 6, L)-D-allofuranose). The coordination mode and conformation of the carbohydrate ligands in 5 and 6 in acetone-d 6 have been determined from an analysis of J HH , J CH , and J CC in complexes formed using site-specific 13 C-labeled D-mannose and D-allose. These coupling data are compared to those measured in 13 C-labeled complex [PtMe 3 L]BF 4 2 (L) 1,2-O-isopropylidene-R-D-glucofuranose) and 1,2-O-isopropylidene-R-D-glucofuranose 3, whose solid-state structures are known, and in 13 C-labeled 1,2;5,6-di-O-isopropylidene-R-D-glucofuranose 4. The preferred furanose ring conformations in 2 and 5 are very similar (3 E/E 4 and E 4 / o E/E 1 , respectively; eastern hemisphere of the pseudorotational itinerary), with platinum coordination involving O3, O5, and O6 of the saccharide. In contrast, the furanose ring of 6 prefers an 4 E/E o / 1 E geometry (western hemisphere of the pseudorotational itinerary) resulting from altered complexation involving O1, O5, and O6. Couplings within the exocyclic fragments of 2, 5, and 6 also support the existence of two different platinum coordination modes. In addition to establishing the structures and conformations of 2, 5, and 6 in solution, one-, two-, and three-bond J CH and J CC observed in these complexes provide new insights into the effect of structure and conformation on the magnitudes of these couplings in saccharides. Weak platinum(IV) complexation with the carbohydrate conformationally restricts the furanose and exocyclic fragment without introducing undesirable structural strain, thereby allowing more reliable correlations between structure and coupling magnitude.
Carbohydrate Research, 1982
ChemInform, Dec 22, 1987
ChemInform Abstract The title trisilylphosphanes are formed as demonstrated for the examples (III... more ChemInform Abstract The title trisilylphosphanes are formed as demonstrated for the examples (III), (IV) and (VI). Their 29Si as well as 31P NMR spectra are recorded.
Acta Crystallographica Section C: Structural Chemistry, May 14, 2019
Free Radical Biology and Medicine, Jun 1, 2000
13 C-NMR spectroscopy was used to record time courses of the metabolism of [1-13 C]-L-ascorbic ac... more 13 C-NMR spectroscopy was used to record time courses of the metabolism of [1-13 C]-L-ascorbic acid (AA) and [2-13 C]-L-ascorbic acid and their dehydro-counterparts (DHAA) by human erythrocytes. Under a range of experimental conditions, but most notably in the absence of glucose in the incubation medium, no 13 C-NMR signal for lactate emerged during any of the 5 h time courses. The NMR resonances that did emerge over time were assigned to diketogulonic (DKG) acid and CO 2. Only very minor resonances from degradation products of DKG appeared from samples that contained physiologically high concentrations of DHAA. These results are in contrast with those in a recent report that lactate is derived from AA in human erythrocytes. However, an explanation for this possible artifact is given.
Carbohydrate Research, Mar 1, 1992
Three isotope-edited n.m.r. methods have been applied to selectively 13C-substituted monosacchari... more Three isotope-edited n.m.r. methods have been applied to selectively 13C-substituted monosaccharides and nucleosides to simplify their spectra and/or measure 1H-1H, 13C-1H, or 13H-13C spin-couplings detected via the labeled site. 1D INADEQUATE spectra allowed the selective detection of the natural-abundance carbons that are spin-coupled to the labeled carbon, and adjustment of the mixing time permitted further discrimination between one-bond and longer-range 13C-13C coupling pathways. Geminal and vicinal 13C-1H coupling constants were determined from the analysis of 1H-1H COSY cross-peaks for those protons coupled to the labeled carbon. Long-range 13C-(HETCOR) and 1H-detected (HMBC) 13C-1H chemical-shift correlation spectra permitted the selective observation of those protons coupled to the labeled site, and JH,H values were measured from data projections. The implications of these methods for structural studies of more complex systems is briefly discussed.
Journal of Comparative Physiology B-biochemical Systemic and Environmental Physiology, Mar 1, 1988
Freeze-tolerance in larvae of Gynaephora groenlandica is enhanced by the accumulation of glycerol... more Freeze-tolerance in larvae of Gynaephora groenlandica is enhanced by the accumulation of glycerol in the winter. Since summer larvae remain freeze-tolerant despite the lack of glycerol, we investigated glycerol metabolism as a function of acclimation and body temperature using noninvasive 13C NMR spectroscopy. Major constituents of hemolymph isolated from cold- and warm-acclimated larvae were identified with the aid of standard NMR spectra and confirmed by TLC and GLC. Spectra obtained on live, warm-acclimated larvae showed the presence of lipids, glycogen, glucose, trehalose and amino acids. Similar spectra of cold-acclimated or previously frozen larvae showed the additional presence of glycerol. In vitro time-lapse 13C spectra of D-[1-13C]glucose added separately to hemolymph or extracted fat body tissue showed that glycerol is synthesized from glucose in the fat body tissue and distributed to the peripheral tissue via hemolymph. In vivo time-lapse 13C spectra of cold- and warm-acclimated larvae were obtained after injection with D-[1-13C]glucose to monitor the production of labeled metabolic intermediates and end-products. [13C]Glycerol was produced between -30 degrees C and 30 degrees C but accumulated only below 5 degrees C. Above 5 degrees C glycerol was degraded and the 13C label incorporated mainly into glycogen. The mechanism underlying temperature control of glycerol biosynthesis and degradation may provide a clue to the role of glycerol in enhancing freeze-tolerance in these insects.
![Research paper thumbnail of Carbon-13 NMR studies of [1-13C]aldoses: empirical rules correlating pyranose ring configuration and conformation with carbon-13 chemical shifts and carbon-13/carbon-13 spin couplings](https://attachments.academia-assets.com/107141400/thumbnails/1.jpg)
](Journal of the American Chemical Society, Jun 1, 1987
o-talose have been synthesized and purified with [I3C]-enrichment (99 atom %) at the anomeric car... more o-talose have been synthesized and purified with [I3C]-enrichment (99 atom %) at the anomeric carbon. I3C NMR spectra (75 MHz) of the natural and enriched compounds have been obtained in *H20, from which 13C-"C couplings to the enriched sites were measured. On the basis of I3C-l3C coupling patterns, I3C chemical shifts for the aldoses were confirmed and some signals (e.g., talose) were reassigned. Complex spectra of enriched compounds were simplified by employing the INADEQUATE method of data collection (spectral editing), and signal assignments to specific tautomers were made in several cases with the aid of selective '3C-decoupling. An empirical method has been developed that predicts 13C chemical shifts in aldopyranose rings and has been used to examine the effect of pyranose structure on I3C chemical shifts. The dependence of I3C-l3C couplings involving C1 on furanose and pyranose ring configuration and conformation has been reexamined, and previous correlations have been modified to accommodate new data.
Acta Crystallographica Section C: Structural Chemistry, Jul 29, 2019
Acta Crystallographica Section C-crystal Structure Communications, Jan 23, 2007
The pseudorotational itinerary of an aldofuranose ring. E and T denote envelope and twist forms, ... more The pseudorotational itinerary of an aldofuranose ring. E and T denote envelope and twist forms, respectively. The preferred furanose conformations in crystalline (I) and (II) are highlighted. organic compounds o140 Kline et al. C 8 H 11 N 3 O 4
Acta Crystallographica Section C: Structural Chemistry, Jan 25, 2019
The crystal structures of 2,3,4,6-tetra-O-benzoyl-β-D-galactopyranosyl-(1→4)-1,2,6-tri-O-benzoyl-... more The crystal structures of 2,3,4,6-tetra-O-benzoyl-β-D-galactopyranosyl-(1→4)-1,2,6-tri-O-benzoyl-β-D-glucopyranose ethyl acetate hemisolvate, C61H50O18·0.5C4H8O2, and 1,2,4,6-tetra-O-benzoyl-β-D-glucopyranose acetone monosolvate, C34H28O10·C3H6O, were determined and compared to those of methyl β-D-galactopyranosyl-(1→4)-β-D-glucopyranoside (methyl β-lactoside) and methyl β-D-glucopyranoside hemihydrate, C7H14O6·0.5H2O, to evaluate the effects of O-benzoylation on bond lengths, bond angles and torsion angles. In general, O-benzoylation exerts little effect on exo- and endocyclic C—C and endocyclic C—O bond lengths, but exocyclic C—O bonds involved in O-benzoylation are lengthened by 0.02–0.04 Å depending on the site of substitution. The conformation of the O-benzoyl side-chains is highly conserved, with the carbonyl O atom either eclipsing the H atom attached to a 2°-alcoholic C atom or bisecting the H—C—H bond angle of an 1°-alcoholic C atom. Of the three bonds that determine the side-chain geometry, the C—O bond involving the alcoholic C atom exhibits greater rotational variability than the remaining C—O and C—C bonds involving the carbonyl C atom. These findings are in good agreement with recent solution NMR studies of the O-acetyl side-chain conformation in saccharides.
Carbohydrate Research, Jun 1, 1987
Chemical methods are described for preparing unenriched and [1-13C]-enriched 5-deoxy- and 5-O-met... more Chemical methods are described for preparing unenriched and [1-13C]-enriched 5-deoxy- and 5-O-methyl-pentoses in the D or L configuration. The 1H-n.m.r. spectra of these compounds have been interpreted, and the 13C-n.m.r. spectra assigned with the aid of 2-D 13C-1H chemical-shift correlation spectroscopy. Tautomeric forms (furanoses, hydrate, and aldehyde) in solution in 2H2O have been quantified with the aid of [1-13C]-enriched derivatives. Spectra of 5-deoxypentoses, 5-O-methylpentoses, and methyl pentofuranosides have been compared, in order to assess the effect of 5-C-deoxygenation and 5-O-methylation on chemical shifts and coupling constants (1H-1H, 13C-1H, and 13C-13C) and on the pentofuranose conformations.
Physical Chemistry Chemical Physics, 2023
The dependence of calculated 1JC1,C2 values on the C1–C2–O2–H torsion angles θ2 in several methyl... more The dependence of calculated 1JC1,C2 values on the C1–C2–O2–H torsion angles θ2 in several methyl aldohexopyranosides.
Accounts of Chemical Research, Aug 11, 2023
ChemInform, Jan 15, 2008
ABSTRACT
Magnetic Resonance in Chemistry, Feb 1, 1988
Adenosine, cytidine, guanosine and uridine were prepared with stereoselective deuteriation at C-5... more Adenosine, cytidine, guanosine and uridine were prepared with stereoselective deuteriation at C-5' and used to assign the prochiral C-5' protons in 300 MHz 'H NMR spectra. In all cases, the more shielded C-5' proton was found to be the pro-R proton. From these assignments, C-4'-C-5' rotamer populations have been estimated, and some discussion of the errors associated with these calculations is given. The relative populations of rotamers in ribonucleosides were found to be affected by structure at C-1, ring conformation and possibly solution pH.
Carbohydrate Research, Mar 1, 2020
Sugar 1,2-orthoesters are by-products of chemical glycosylation reactions that can be subsequentl... more Sugar 1,2-orthoesters are by-products of chemical glycosylation reactions that can be subsequently rearranged in situ to give trans glycosides. They have been used as donors in the synthesis of the latter glycosides with good regio- and stereo-selectivity. Alkyl α-(1 → 2) linked mannopyranosyl disaccharides have been reported as the major products from the rearrangement of mannopyranosyl orthoesters. Recent studies in this laboratory have shown that α-(1 → 2) linked mannopyranosyl di-, tri- and tetrasaccharides can be obtained in one step from mannopyranosyl allyl orthoester under optimized reaction conditions. In addition to the expected mono- and disaccharides (56%), allyl 2,3,4,6-tetra-O-acetyl-α-D-mannopyranosyl-(1 → 2)-3,4,6-tri-O-acetyl-α-D-mannopyranosyl-(1 → 2)-tri-O-acetyl-α-D-mannopyranoside and allyl 2,3,4,6-tetra-O-acetyl-α-D-mannopyranosyl-(1 → 2)-3,4,6-tri-O-acetyl-α-D-mannopyranosyl-(1 → 2)-3,4,6-tri-O-acetyl-α-D-mannopyranosyl-(1 → 2)-3,4,6-tri-Oacetyl-α-D-mannopyranoside were obtained in 23% and 6% isolated yields, respectively, from the oligomerization of a β-D-mannopyranosyl allyl 1,2-orthoester, along with small amounts of higher DP oligomers. Possible mechanisms for the oligomerization and side reactions are proposed based on NMR and mass spectrometric data.
Journal of Organic Chemistry, Mar 20, 2007
Reaction of a galactosylated 2-C-(hydroxymethyl)-tetrofuranose with paramolybdate ion-exchange re... more Reaction of a galactosylated 2-C-(hydroxymethyl)-tetrofuranose with paramolybdate ion-exchange resin in aqueous solution at 67°C gave an equililibrium mixture containing the reactant aldofuranose (42%) and a 2-ketopentofuranose galactosylated at O1 (58%). Observation of this stereospecific rearrangement supports prior arguments that substituents at C2 of the branched-chain aldofuranose reactant are located in a sterically accessible pocket of the putative dimolybdatesaccharide reactive complex during epimerization. This rearrangement provides a new and convenient route to 2-ketosugars glycosylated at the exocyclic C1 position. Carbohydrate complexes with cations and anions in aqueous solution have been studied extensively by Angyal and others 1,2 and form the basis of convenient chromatographic methods to separate and purify saccharides. 3-5 Ion binding strength is determined partly by the relative configuration of hydroxyl ligands on the saccharide. For example, complexation of the divalent Ca 2+ ion is strongest for aldopyranosyl rings containing contiguous ax-eq-ax arrangements, whereas the presence of cis-1,2-OH groups is important for cation binding to aldofuranosyl rings. Cation binding to sugars is relatively weak, however, and the biological implications of these interactions remain unclear. Anions such as borate, tungstate, arsenate, and molybdate bind saccharides strongly, but interestingly, the former three produce stable, unreactive complexes, whereas the latter forms a highly reactive complex that promotes an unusual, stereospecific rearrangement of the carbon skeleton. 6 For example, the addition of catalytic amounts of resin-bound molybdate 7 to an aqueous solution of D-[1-13 C]erythrose 1 (pH 4.2) at 90°C yields an equilibrium mixture of 1 (∼35%) and D-[2-13 C]threose 2 (∼65%) after ∼3 h (Scheme 1). C2-Epimerization occurs with C1-C2 transposition and appears to proceed via an acyclic dimolybdate-saccharide intermediate. 6 Recent work has shown that the aldehydic proton of 1 can be replaced by CH 2 OH, CH 3 , or CH 2 OPh substituents without compromising the viability of the transformation. 8 2-C-(Methyl)-D-erythrose 3 and 1-deoxy-D-xylulose 4 are thus interconverted by molybdate anion in aqueous solution, with the latter highly favored at equilibrium (Scheme 1). Given the tolerance for simple functional groups at C2 of branched-chain aldotetroses, we examined whether the rearrangement would proceed with a glycosyl residue present at this position. Methyl 2-C-(hydroxymethyl)-2,3-O-isopropylidene-D-erythrofuranoside 5 8 was prepared and condensed with 2,3,4,6-tetra-O-acetyl-R-D-galactopyranosyl bromide 6. Deprotection afforded-D-galactopyranosyl-(1f2C)-2-C-(hydroxymethyl)-D-erythrose (7) (Scheme 2). The 1 H NMR spectrum of 7 (Figure S1, Supporting Information) contained two singlets at 5.234 and 5.243 ppm, which were assigned to the furanose anomeric protons H1 (Table 1). Signal integration gave a 42/58 ratio, with the downfield H1 signal more intense. Two additional anomeric 1 H signals at 4.436 and 4.403 ppm appeared as doublets with 3 J H1′,H2′) 7.8 Hz. These signals were assigned to H1′ of the Gal residue. The relatively large 3 J H1′,H2′ values show that the linkage has the-configuration. Anomeric carbon signals were observed at 106.31, 105.95, 104.16, and 99.98 ppm (Figure S2, Table 1). The former two correlated with the Gal H1′ signals, and the latter two with the anomeric furanose signals (i.e., 104.16/5.234 and 99.98/5.243
Journal of Organic Chemistry, Jun 1, 2000
The reaction of D-mannose and D-allose with [PtMe 3 (Me 2 CO) 3 ]BF 4 1 in acetone affords comple... more The reaction of D-mannose and D-allose with [PtMe 3 (Me 2 CO) 3 ]BF 4 1 in acetone affords complexes [PtMe 3 L]BF 4 5 and 6 (5, L) R-D-mannofuranose; 6, L)-D-allofuranose). The coordination mode and conformation of the carbohydrate ligands in 5 and 6 in acetone-d 6 have been determined from an analysis of J HH , J CH , and J CC in complexes formed using site-specific 13 C-labeled D-mannose and D-allose. These coupling data are compared to those measured in 13 C-labeled complex [PtMe 3 L]BF 4 2 (L) 1,2-O-isopropylidene-R-D-glucofuranose) and 1,2-O-isopropylidene-R-D-glucofuranose 3, whose solid-state structures are known, and in 13 C-labeled 1,2;5,6-di-O-isopropylidene-R-D-glucofuranose 4. The preferred furanose ring conformations in 2 and 5 are very similar (3 E/E 4 and E 4 / o E/E 1 , respectively; eastern hemisphere of the pseudorotational itinerary), with platinum coordination involving O3, O5, and O6 of the saccharide. In contrast, the furanose ring of 6 prefers an 4 E/E o / 1 E geometry (western hemisphere of the pseudorotational itinerary) resulting from altered complexation involving O1, O5, and O6. Couplings within the exocyclic fragments of 2, 5, and 6 also support the existence of two different platinum coordination modes. In addition to establishing the structures and conformations of 2, 5, and 6 in solution, one-, two-, and three-bond J CH and J CC observed in these complexes provide new insights into the effect of structure and conformation on the magnitudes of these couplings in saccharides. Weak platinum(IV) complexation with the carbohydrate conformationally restricts the furanose and exocyclic fragment without introducing undesirable structural strain, thereby allowing more reliable correlations between structure and coupling magnitude.
Carbohydrate Research, 1982
ChemInform, Dec 22, 1987
ChemInform Abstract The title trisilylphosphanes are formed as demonstrated for the examples (III... more ChemInform Abstract The title trisilylphosphanes are formed as demonstrated for the examples (III), (IV) and (VI). Their 29Si as well as 31P NMR spectra are recorded.
Acta Crystallographica Section C: Structural Chemistry, May 14, 2019
Free Radical Biology and Medicine, Jun 1, 2000
13 C-NMR spectroscopy was used to record time courses of the metabolism of [1-13 C]-L-ascorbic ac... more 13 C-NMR spectroscopy was used to record time courses of the metabolism of [1-13 C]-L-ascorbic acid (AA) and [2-13 C]-L-ascorbic acid and their dehydro-counterparts (DHAA) by human erythrocytes. Under a range of experimental conditions, but most notably in the absence of glucose in the incubation medium, no 13 C-NMR signal for lactate emerged during any of the 5 h time courses. The NMR resonances that did emerge over time were assigned to diketogulonic (DKG) acid and CO 2. Only very minor resonances from degradation products of DKG appeared from samples that contained physiologically high concentrations of DHAA. These results are in contrast with those in a recent report that lactate is derived from AA in human erythrocytes. However, an explanation for this possible artifact is given.
Carbohydrate Research, Mar 1, 1992
Three isotope-edited n.m.r. methods have been applied to selectively 13C-substituted monosacchari... more Three isotope-edited n.m.r. methods have been applied to selectively 13C-substituted monosaccharides and nucleosides to simplify their spectra and/or measure 1H-1H, 13C-1H, or 13H-13C spin-couplings detected via the labeled site. 1D INADEQUATE spectra allowed the selective detection of the natural-abundance carbons that are spin-coupled to the labeled carbon, and adjustment of the mixing time permitted further discrimination between one-bond and longer-range 13C-13C coupling pathways. Geminal and vicinal 13C-1H coupling constants were determined from the analysis of 1H-1H COSY cross-peaks for those protons coupled to the labeled carbon. Long-range 13C-(HETCOR) and 1H-detected (HMBC) 13C-1H chemical-shift correlation spectra permitted the selective observation of those protons coupled to the labeled site, and JH,H values were measured from data projections. The implications of these methods for structural studies of more complex systems is briefly discussed.
Journal of Comparative Physiology B-biochemical Systemic and Environmental Physiology, Mar 1, 1988
Freeze-tolerance in larvae of Gynaephora groenlandica is enhanced by the accumulation of glycerol... more Freeze-tolerance in larvae of Gynaephora groenlandica is enhanced by the accumulation of glycerol in the winter. Since summer larvae remain freeze-tolerant despite the lack of glycerol, we investigated glycerol metabolism as a function of acclimation and body temperature using noninvasive 13C NMR spectroscopy. Major constituents of hemolymph isolated from cold- and warm-acclimated larvae were identified with the aid of standard NMR spectra and confirmed by TLC and GLC. Spectra obtained on live, warm-acclimated larvae showed the presence of lipids, glycogen, glucose, trehalose and amino acids. Similar spectra of cold-acclimated or previously frozen larvae showed the additional presence of glycerol. In vitro time-lapse 13C spectra of D-[1-13C]glucose added separately to hemolymph or extracted fat body tissue showed that glycerol is synthesized from glucose in the fat body tissue and distributed to the peripheral tissue via hemolymph. In vivo time-lapse 13C spectra of cold- and warm-acclimated larvae were obtained after injection with D-[1-13C]glucose to monitor the production of labeled metabolic intermediates and end-products. [13C]Glycerol was produced between -30 degrees C and 30 degrees C but accumulated only below 5 degrees C. Above 5 degrees C glycerol was degraded and the 13C label incorporated mainly into glycogen. The mechanism underlying temperature control of glycerol biosynthesis and degradation may provide a clue to the role of glycerol in enhancing freeze-tolerance in these insects.
Journal of the American Chemical Society, Jun 1, 1987
o-talose have been synthesized and purified with [I3C]-enrichment (99 atom %) at the anomeric car... more o-talose have been synthesized and purified with [I3C]-enrichment (99 atom %) at the anomeric carbon. I3C NMR spectra (75 MHz) of the natural and enriched compounds have been obtained in *H20, from which 13C-"C couplings to the enriched sites were measured. On the basis of I3C-l3C coupling patterns, I3C chemical shifts for the aldoses were confirmed and some signals (e.g., talose) were reassigned. Complex spectra of enriched compounds were simplified by employing the INADEQUATE method of data collection (spectral editing), and signal assignments to specific tautomers were made in several cases with the aid of selective '3C-decoupling. An empirical method has been developed that predicts 13C chemical shifts in aldopyranose rings and has been used to examine the effect of pyranose structure on I3C chemical shifts. The dependence of I3C-l3C couplings involving C1 on furanose and pyranose ring configuration and conformation has been reexamined, and previous correlations have been modified to accommodate new data.
Acta Crystallographica Section C: Structural Chemistry, Jul 29, 2019
Acta Crystallographica Section C-crystal Structure Communications, Jan 23, 2007
The pseudorotational itinerary of an aldofuranose ring. E and T denote envelope and twist forms, ... more The pseudorotational itinerary of an aldofuranose ring. E and T denote envelope and twist forms, respectively. The preferred furanose conformations in crystalline (I) and (II) are highlighted. organic compounds o140 Kline et al. C 8 H 11 N 3 O 4
Acta Crystallographica Section C: Structural Chemistry, Jan 25, 2019
The crystal structures of 2,3,4,6-tetra-O-benzoyl-β-D-galactopyranosyl-(1→4)-1,2,6-tri-O-benzoyl-... more The crystal structures of 2,3,4,6-tetra-O-benzoyl-β-D-galactopyranosyl-(1→4)-1,2,6-tri-O-benzoyl-β-D-glucopyranose ethyl acetate hemisolvate, C61H50O18·0.5C4H8O2, and 1,2,4,6-tetra-O-benzoyl-β-D-glucopyranose acetone monosolvate, C34H28O10·C3H6O, were determined and compared to those of methyl β-D-galactopyranosyl-(1→4)-β-D-glucopyranoside (methyl β-lactoside) and methyl β-D-glucopyranoside hemihydrate, C7H14O6·0.5H2O, to evaluate the effects of O-benzoylation on bond lengths, bond angles and torsion angles. In general, O-benzoylation exerts little effect on exo- and endocyclic C—C and endocyclic C—O bond lengths, but exocyclic C—O bonds involved in O-benzoylation are lengthened by 0.02–0.04 Å depending on the site of substitution. The conformation of the O-benzoyl side-chains is highly conserved, with the carbonyl O atom either eclipsing the H atom attached to a 2°-alcoholic C atom or bisecting the H—C—H bond angle of an 1°-alcoholic C atom. Of the three bonds that determine the side-chain geometry, the C—O bond involving the alcoholic C atom exhibits greater rotational variability than the remaining C—O and C—C bonds involving the carbonyl C atom. These findings are in good agreement with recent solution NMR studies of the O-acetyl side-chain conformation in saccharides.