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.

STEREOCHEMICAL STUDIES: V. REARRANGEMENTS ACCOMPANYING ATTEMPTS TO EPIMERIZE 4-OXA-3-OXO-5α-CHOLESTANE AND 4-OXA-3-OXO-5β-CHOLESTANE BY BREWSTER AND KUCERA'S METHOD

1966 ◽  
Vol 44 (3) ◽  
pp. 279-295 ◽  
Author(s):  
W. H. Lunn ◽  
J. T. Edward ◽  
Seymour Meyerson
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Structural Features ◽  
Ring Structure ◽  
Skeletal Rearrangement ◽  
Nuclear Magnetic Resonance Spectra ◽  
Highly Sensitive ◽  
Hydrolysis Of ◽  
Magnetic Resonance Spectra ◽  
Nuclear Magnetic

Epimerization of 4-oxa-3-oxo-5α-cholestane by Brewster and Kucera's method gave only a 23% yield of the 5β-lactone; several other compounds were formed, apparently via skeletal rearrangement during hydrolysis of the tosylate. The attempted epimerization of 4-oxa-3-oxo-5β-cholestane gave mainly unsaturated acids, but no 5α-lactone (a small amount of skeletal rearrangement also occurred). Both epimers undergo rearrangement to γ-lactones when treated with trifluoroacetic acid.Mass spectra, used in conjunction with infrared and nuclear magnetic resonance spectra and other data to make structural assignments, were found to be highly sensitive to certain structural features. In particular, they can usually distinguish sharply between molecules that contain a pendant ring structure and those that do not.

The preparation of 2-Fluoro-5-nitrobenzonitrile and the proton magnetic resonance spectra of some compounds containing the N-(2-Cyano-4-nitrophenyl) group

1967 ◽  
Vol 20 (8) ◽  
pp. 1663 ◽  
Author(s):  
JFK Wilshire
Keyword(s):  
Amino Acids ◽  
Magnetic Resonance ◽  
Nitro Group ◽  
Proton Magnetic Resonance ◽  
Cyano Group ◽  
Aromatic Nucleus ◽  
Heteroaromatic Compounds ◽  
Magnetic Resonance Spectra

2-Fluoro-5-nitrobenzonitrile, an analogue of 1-fluoro-2,4- dinitrobenzene, in which the 2-nitro group has been replaced by a cyano group, has been prepared and made to react with several amines, amino acids, and NH-heteroaromatic compounds. The proton magnetic resonance spectra of some of the resultant N-(2-cyano-4-nitrophenyl) derivatives were compared with the spectra of the corresponding N-(2,4- dinitrophenyl) derivatives and furnish further evidence that the ortho nitro group of the latter derivatives is rotated out of the plane of the aromatic nucleus.

Investigation and Identification of the Bromination Products of Dimethoxyamphetamines

1976 ◽  
Vol 59 (5) ◽  
pp. 1162-1169
Author(s):  
Keith Bailey ◽  
Denise R Gagné ◽  
Richard K Pike
Keyword(s):  
Magnetic Resonance ◽  
Qualitative Analysis ◽  
Thin Layer ◽  
Thin Layer Chromatography ◽  
Infrared Spectra ◽  
Proton Magnetic Resonance ◽  
Positive Identification ◽  
Aromatic Bromination ◽  
Layer Chromatography ◽  
Magnetic Resonance Spectra

Abstract The qualitative analysis of the aromatic bromination products of the 6 isomeric dimethoxyamphetamines and their hydrochloride or hydrobromide salts is described. Their ultraviolet, mass, and proton magnetic resonance spectra are not sufficiently different for distinction but infrared spectra allow a positive identification to be made and reference spectra are provided for the bromination products of 2,4-, 2,5-, 2,6-, 4,5-, and 3,5-dimethoxyamphetamines. The application of gas-liquid and thin layer chromatography for the analysis of these products is discussed. The bromination of 2,3-dimethoxyamphetamine consistently gave mixtures which could not be separated satisfactorily; spectra are included for completeness of the comparison of products.

Sign in / Sign up

Export Citation Format

Share Document