METHANOLYSIS OF CARBOHYDRATE ORTHOACETATES

1963 ◽  
Vol 41 (3) ◽  
pp. 555-561 ◽  
Author(s):  
A. S. Perlin
Keyword(s):  
Magnetic Resonance ◽  
Spectral Data ◽  
Methyl Ether ◽  
Proton Magnetic Resonance ◽  
Acyl Migration ◽  
Acetate Group ◽  
Marked Contrast ◽  
Aqueous Acid ◽  
Acid Methanolysis ◽  
Hydrolysis Of

Acid methanolysis of D-mannose 1,2-(methyl orthoacetate) 3,4,6-triacetate (I) yields mainly 3,4,6-tri-O-acetyl-D-mannose (II). D-glucose 1,2-(ethyl orthoacetate) 3,4,6-triacetate (VIII) yields 3,4,6-tri-O-acetyl-D-glucose and methyl 3,4,6-tri-O-acetyl-β-D-glucopyranoside. The rate of methanolysis of II differs little from that of VIII, in marked contrast to the relative rates of hydrolysis of these compounds in aqueous acid. Several concurrent reactions appear to take place in methanol initiated by protonation at different positions on the orthoester ring.During isolation, II is converted partially to 2,4,6-tri-O-acetyl-D-mannose (VI), a novel instance of acyl migration in the sugar series. Structural assignments for these two triacetates are based on chemical and proton magnetic resonance spectral data. The 2-acetate group of VI migrates during methylation, both II and VI yielding the same 2-O-methyl ether.

1,4-Cycloheptadienes: preparation and comparison of their proton magnetic resonance spectra with those of the corresponding cycloheptatrienes

1977 ◽  
Vol 55 (2) ◽  
pp. 251-258 ◽  
Author(s):  
Ivan Pikulik ◽  
Ronald F. Childs
Keyword(s):  
Magnetic Resonance ◽  
Good Yield ◽  
Proton Magnetic Resonance ◽  
Copper Complexes ◽  
Ring Current ◽  
Catalytic Reduction ◽  
Azo Compounds ◽  
Pmr Spectra ◽  
Basic Hydrolysis ◽  
Hydrolysis Of

A general route to 3-substituted cyclohepta-1,4-dienes is described in this paper. 7-Substituted cycloheptatrienes were used as starting materials and these were reacted with 4-phenyl-1,2,4-triazoline-3,5-dione to give 4 + 2 cycloaddition products of the norcaradiene form of the cycloheptatrienes. Catalytic reduction of these adducts gave 9-substituted 4-phenyl-2,4,6-triazatetracyclo[5.3.2.02,6.08,10]dodeca-3,5-diones in good yield. Basic hydrolysis of the hetero-cyclic ring of these products followed by Cu2+ oxidation of the resulting hydrazo compounds gave the copper complexes of substituted 6,7-diazatricyclo[3.2.2.02,4]non-6-enes. The azo compounds, formed on decomplexation of the copper complexes, readily lost nitrogen to give 3-substituted cyclohepta-l,4-dienes. Care had to be taken during these last steps as the cyclo-heptadienes with carboxylate substituents very readily isomerized to the conjugated isomers. The pmr spectra of the cyclohepta-l,4-dienes and related cycloheptatrienes are compared and discussed in terms of the presence of an induced diamagnetic ring current in the latter systems.

scholarly journals Changes in proton-magnetic-resonance spectra during aminolysis and enzymic hydrolysis of cephalosporins

1970 ◽  
Vol 116 (3) ◽  
pp. 385-395 ◽  
Author(s):  
J. M. T. Hamilton-Miller ◽  
Eva Richards ◽  
E. P. Abraham
Keyword(s):  
Magnetic Resonance ◽  
Proton Magnetic Resonance ◽  
Structural Changes ◽  
Ring Structure ◽  
Reaction Products ◽  
Enzymic Hydrolysis ◽  
Lactam Ring ◽  
Group 5 ◽  
Hydrolysis Of ◽  
Magnetic Resonance Spectra

1. Changes in proton-magnetic-resonance spectra were followed during the reaction of cephalosporins, deacetylcephalosporins, deacetoxycephalosporins and a Δ2-cephalosporin with ND3 in D2O. 2. Changes in proton-magnetic-resonance spectra were also followed during the hydrolysis of a cephalosporin and a deacetylcephalosporin in D2O with a β-lactamase. 3. Structures for the reaction products are proposed. 4. The signals obtained after aminolysis of the β-lactam ring of a cephalosporin indicate that the reaction is accompanied by expulsion of the acetoxy group as acetate, formation of a double bond in the Δ4-position and the appearance of an exocyclic methylene group. 5. Aminolysis of deacetyl- and deacetoxycephalosporins can occur without immediate structural changes in the dihydrothiazine ring. 6. In contrast, the ring structure of the first product of enzymic hydrolysis of a deacetylcephalosporin is apparently identical with that of the product of aminolysis of the cephalosporin itself.

220 MHz spectra of heparin, chondroitins, and other mucopolysaccharides

1970 ◽  
Vol 48 (14) ◽  
pp. 2260-2268 ◽  
Author(s):  
A. S. Perlin ◽  
B. Casu ◽  
G. R. Sanderson ◽  
L. F. Johnson
Keyword(s):  
Hyaluronic Acid ◽  
Magnetic Resonance ◽  
Spectral Data ◽  
Uronic Acid ◽  
Proton Magnetic Resonance ◽  
Keratan Sulfate ◽  
General View ◽  
Model Compounds ◽  
Minor Constituents ◽  
Magnetic Resonance Spectra

Characteristics of proton magnetic resonance spectra of heparins at 220 MHz, coupled with spectral data for model compounds and with information obtained chemically, indicate that heparins are composed principally of (1 → 4)-linked α-L-idopyranosyluronic acid residues (3) and 2-amino-2-deoxy-α-D-glucopyranosyl residues (1); also, that sulfate groups are located at position -2 and -6 of 1, and -2 of 3. D-Glucopyranosyluronic acid residues (2) appear to be minor constituents, which is at variance with all structures that have been proposed previously for heparin.Spectra of chondroitins A, B, and C, which are readily distinguishable, are in close accord with formulae that have been proposed for these mucopolysaccharides; on the same basis, the spectrum of keratan sulfate is less consistent. Hyaluronic acid affords a poorly resolved though, nonetheless, distinctive spectrum. The general view that mucopolysaccharides are constituted basically of residues of hexosamine and uronic acid in equimolar proportion receives support from the current findings. However, heparitin appears to possess a more heterogeneous type of structure than do these other polymers.

Cancentrine. V. The 13C magnetic resonance spectra of cancentrine and some derivatives; the structure of 10-oxocancentrine

1978 ◽  
Vol 56 (18) ◽  
pp. 2467-2471 ◽  
Author(s):  
Herbert L. Holland ◽  
Donald W. Hughes ◽  
David B. MacLean ◽  
Russell G. A. Rodrigo
Keyword(s):  
Magnetic Resonance ◽  
Spectral Data ◽  
Methyl Ether ◽  
Resonance Spectrum ◽  
Chemical Shifts ◽  
Mass Spectral Data ◽  
Mass Spectral ◽  
H Nmr ◽  
First Time ◽  
Magnetic Resonance Spectra

The 13C magnetic resonance spectrum of cancentrine is reported. Assignments of chemical shifts have been made by comparison of the cancentrine spectrum with the published spectra of codeine, codeinone, and cularine and with the spectra reported here for the first time of 9,10-dihydrocancentrine methine-O-methyl ether and 10-oxocodeinone. The spectral data so obtained have been used to interpret the 13C spectrum of 10-oxocancentrine, a new alkaloid of the cancentrine family, and to verify the structure deduced for it from 1H nmr, ir, uv, and mass spectral data.

Quaternary Nitrogen Heterocycles. V. Substituent Effects on the Equilibrium Constants for Pseudobase Formation from Quinolinium and Isoquinolinium Cations

1974 ◽  
Vol 52 (6) ◽  
pp. 962-974 ◽  
Author(s):  
John W. Bunting ◽  
William G. Meathrel
Keyword(s):  
Aqueous Solution ◽  
Magnetic Resonance ◽  
Spectral Data ◽  
Proton Magnetic Resonance ◽  
Equilibrium Constants ◽  
Nitrogen Heterocycles ◽  
Substituent Effects ◽  
Stopped Flow ◽  
Substituent Constant ◽  
Quaternary Nitrogen

Equilibrium constants (pKROH) have been measured for pseudobase formation from the 1-methyl-x-nitroquinolinium cations (x = 5–8), the N,N′-dimethyl-1,5-, -1,6-, and -2,7-naphthyridinium dications and various N-substituted quinolinium, isoquinolinium, 5-nitroisoquinolinium, and 1,8-naphthyridinium cations. The pKROH values for N-substituted 5-nitroisoquinolinium and 1,8-naphthyridinium cations are correlated by the equations pKROH = −3.7σ* + 11.6 and pKROH = −4.9σ* + 12.5, respectively (σ* is Taft's substituent constant for the substituent on nitrogen).Proton magnetic resonance and u.v. spectral data have been used to assign the structures of the pseudobases formed from each of the above cations. In several cases ylide formation rather than pseudobase formation has been observed. The N,N′-dimethylnaphthyridinium dications are shown to form zwitterionic alkoxide ions in strongly basic aqueous solution, rather than undergoing attack by a second hydroxide ion.Equilibration between cation and pseudobase occurs at rates near or beyond the limit of the stopped-flow technique for all the above cations, except the 2-cyanomethyl-5-nitroisoquinolinium cation. An analysis of the pH-rate profiles for reversible pseudobase formation from this latter cation is given.

STUDIES ON CHITAN (β-(1 → 4)-LINKED 2-ACETAMIDO-2-DEOXY-D-GLUCAN) FIBERS OF THE DIATOM THALASSIOSIRA FLUVIATILIS HUSTEDT: II. PROTON MAGNETIC RESONANCE, INFRARED, AND X-RAY STUDIES

1966 ◽  
Vol 44 (19) ◽  
pp. 2269-2281 ◽  
Author(s):  
Michael Falk ◽  
D. G. Smith ◽  
J. McLachlan ◽  
A. G. McInnes
Keyword(s):  
Magnetic Resonance ◽  
Infrared Spectrum ◽  
Proton Magnetic Resonance ◽  
Distinct Species ◽  
Crystalline Modification ◽  
X Ray Diffraction ◽  
X Ray ◽  
Infrared Studies ◽  
Hydrolysis Of ◽  
Anomeric Center

The extracellular fibers attached to the diatom Thalassiosirafluviatilis have been shown to be pure β-(1 → 4)-linked 2-acetamido-2-deoxy-D-glucan. This polysaccharide was given the systematic trivial name chitan to distinguish it from chitin, which is not a chemically distinct species and which has a radically different X-ray diffraction pattern and infrared spectrum. Proton magnetic resonance studies on the acid hydrolysis of chitan have established that the hydrolysis occurred in three distinct steps: (a) the degradation of the polysaccharide to smaller polymeric units, (b) the production of N-acetylglucosamine from the latter, and (c) the conversion of N-acetylglucosamine into glucosamine and acetic acid. X-ray and infrared studies have shown that chitan has a different macrostructure from that of arthropod chitin. Chitan is completely crystalline and can be converted irreversibly into a form indistinguishable from that of chitin by treatment with hot aqueous lithium thiocyanate. Boiling chitan in water converts it into a second crystalline modification, possibly a hydrate, which can be reconverted into the starting material by drying invacuo. The exceptionally sharp infrared spectrum of chitan allows a more unequivocal assignment of a number of bands common to chitan and chitin, and provides information about the nature of the bands at 1 626 and 1 656 cm−1 in the spectrum of chitin. The correlation of the bands in the region of 840 to 890 cm−1 with the configuration at the anomeric center of glycopyranose derivatives is discussed.

Librations Around the C(S)—Phenyl Bond in N-Thiobenzoylmorpholines Observed by 220 MHz Proton Magnetic Resonance Spectroscopy

1975 ◽  
Vol 53 (21) ◽  
pp. 3315-3318 ◽  
Author(s):  
Adrian O. Fulea ◽  
Peter J. Krueger
Keyword(s):  
Magnetic Resonance ◽  
Magnetic Resonance Spectroscopy ◽  
Spectral Data ◽  
Proton Magnetic Resonance ◽  
Proton Magnetic Resonance Spectroscopy ◽  
Resonance Spectroscopy ◽  
Thioamide Group ◽  
Related Compounds

The 220 MHz p.m.r. spectra of 4-(4′-nitrothiobenzoyl)-2,6-dimethylmorpholine (1) provide evidence for the progressive freezing of the librations of the thioamide group around the C(S)—Ph bond as the temperature is lowered. This is supported by spectral data on related compounds in which the aromatic and hetero-ring substituents are altered.

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