Minor diterpene components of the defense secretion from the frontal gland of soldiers of the species Nasutitermes costalis (HOLMGREN)

1984 ◽  
Vol 49 (9) ◽  
pp. 2024-2039 ◽  
Author(s):  
Irena Valterová ◽  
Miloš Buděšínský ◽  
František Tureček ◽  
Jan Vrkoč
Keyword(s):  
Acid Methyl Ester ◽  
Mass Spectral Fragmentation ◽  
Stable Conformation ◽  
Relative Configuration ◽  
Mass Spectral ◽  
Defense Secretion ◽  
Alternative Structures ◽  
H Nmr ◽  
Nasutitermes Costalis ◽  
Hydroxy Groups

Three minor components of the defense secretion from soldiers of the species Nasutermes costalis (HOLMGREN) have been isolated and characterized by means of spectral methods. The first component was identified as 1(15),8(19)-trinervitadien-9β-ol (III), known to occur with the subfamily Nasutitermitinae. For the second component two alternative structures IVa, IVb have been tentatively suggested, both with the 7,16-secotrinervitane skeleton. The third component was determined as 5β,9β-diacetoxy-2-oxo-11(12)kempen-20-oic acid (VII). The kempene skeleton was established on the basis of the 13C NMR spectrum and mass spectral fragmentation of the acid methyl ester. The relative configuration, together with a probable conformation of the tetracyclic framework were determined by 1H NMR. Two major tricyclic components, 1(15),8(19)-trinervitadien-2α,3β-diol (I) and 1(15),8(19)-trinervitadien-2α,3α-diol (II), were further characterized as mono and diacetates. Different rates of acetylation of the hydroxy groups in these diols provided evidence of stable conformation of the six-membered ring within the trinervitane skeleton.

Triazolopyridine nucleosides. II. Glycosylations of 3-oxo-s-triazolo[4,3-a]pyridines with accompanying conversions into 2-oxo-s-triazolo[1,5-a]pyridine nucleosides

1977 ◽  
Vol 55 (5) ◽  
pp. 831-840 ◽  
Author(s):  
Brian Maurice Lynch ◽  
Suresh Chandra Sharma
Keyword(s):  
General Structure ◽  
Spectroscopic Properties ◽  
Mass Spectral Fragmentation ◽  
Mass Spectral ◽  
H Nmr ◽  
Pyridine Nitrogen ◽  
Methyl Derivatives ◽  
Fragmentation Patterns ◽  
Ribose Moiety ◽  
C Nmr

3-Oxo-s-triazolo[4,3-a]pyridine and various C-methyl derivatives (general structure 1) have been converted into the 2-β-D-ribofuranosyl species 2 and thence 4 via Friedel–Crafts catalyzed reaction with tetra-O-acetyl-β-D-ribofuranose, followed by deblocking. During the course of these reactions, rearrangements into the isomeric 3-β-D-ribofuranosyl-2-oxo-s-triazolo[1,5-a]-pyridines occur through ring-opening of the pyridine rings yielding species 3 and 5. The proportion of rearrangement products is dependent upon the position and number of the C-methyl substituents.Structural assignments for these compounds are based upon comparisons of spectroscopic properties (1H nmr, 13C nmr, uv) with model compounds from each isomeric series; structural assignments for these models are based on unequivocal mass-spectral fragmentation patterns. Unlike related triazolopyridine nucleosides with the ribose moiety attached to a pyridine nitrogen (Lynch and Sharma (1976)), there are no unusual aspects in the conformations of the nueleosides of types 4 and 5.

Photochemistry of halogenated benzene derivatives. Part VIII. Photoformation of 2-methyl-4,5,6,7-tetrachlorobenzoxazole from pentachlorophenol in water–acetonitrile

1987 ◽  
Vol 65 (9) ◽  
pp. 2223-2233 ◽  
Author(s):  
Ghulam Ghaus Choudhry ◽  
Norma Jean Graham ◽  
G. R. Barrie Webster
Keyword(s):  
Nmr Spectroscopy ◽  
Chemical Yield ◽  
Polarization Transfer ◽  
Benzene Derivatives ◽  
Mass Spectral Fragmentation ◽  
Molecular Ion ◽  
Mass Spectral ◽  
Methanolic Solution ◽  
H Nmr ◽  
C Nmr

Photolysis of a solution of pentachlorophenol (1) in H2O–CH3CN (2:3 v/v) was conducted on a synthetic scale using wavelengths ≥290 nm. After changing the pH of the photolyzate of 1 to ≥12, the photoproduct 2-methyl-4,5,6,7-tetrachloro-benzoxazole (2) was extracted with n-hexane. The product 2 was crystallized from methanolic solution. Ultraviolet, IR, FT-1H-NMR, proton-decoupled normal FT-13C-NMR, and proton-decoupled DEPT (distortionless enhancement by polarization transfer) sequence FT-13C-NMR spectroscopy were used to identify photoproduct 2 as 2-methyl-4,5,6,7-tetrachlorobenzoxazole. A mechanism for the photoformation of benzoxazole 2 from 1 is proposed. 3,4,5,6-Tetrachlorocyclohexa-3,5-diene-1,2-ketocarbene formed from 2-hydroxy-3,4,5,6-tetrachlorophenyl radical is suggested as key intermediate involved in the generation of oxazole 2 from phenol 1. The chemical yield of 2 on the basis of 1 was ca. 1%. A mechanism is proposed to explain the mass spectral fragmentation of 2 via the losses of Ċl,:C=O, Cl—Ċ=O, CH3—Ċ=O, CH3CN, and C3H3ClNO species from the parent molecular ion.

scholarly journals NMR and Mass Spectroscopic Studies on Catharine

1985 ◽  
Vol 40 (4) ◽  
pp. 543-545 ◽  
Author(s):  
◽  
Irshad Ali ◽  
M. Iqbal Chaudhary
Keyword(s):  
Room Temperature ◽  
Spectroscopic Studies ◽  
Temperature Dependent ◽  
Mass Spectral Fragmentation ◽  
Mass Spectral ◽  
H Nmr ◽  
Temperature Dependent Study ◽  
C Nmr

The 13C NMR of Catharine is reported. A temperature-dependent study of the 1H NMR of Catharine indicates that it exists as two conformers at room temperature. At higher temperatures, the distinction between the two conformers disappears with the higher rate of equilibration. The mass spectral fragmentation of Catharine as established by link scan measurements is also re­ported.

Alkaloids from Buxus sempervirens L. III. Mass spectral fragmentation

1965 ◽  
Vol 30 (8) ◽  
pp. 2869-2874 ◽  
Author(s):  
L. Dolejš ◽  
V. Hanuš ◽  
Z. Votický ◽  
J. Tomko
Keyword(s):  
Mass Spectral Fragmentation ◽  
Mass Spectral ◽  
Buxus Sempervirens

Mass Spectra of β-Keto Esters

1972 ◽  
Vol 50 (16) ◽  
pp. 2707-2710 ◽  
Author(s):  
Larry Weiler
Keyword(s):  
Mass Spectra ◽  
Carbonyl Groups ◽  
Mass Spectral Fragmentation ◽  
Mass Spectral ◽  
Keto Esters ◽  
Fragmentation Patterns

The mass spectra of several γ-substituted β-keto esters have been recorded and interpreted. The fragmentation patterns are compared to those of α-substituted β-keto esters and are found to be very useful in differentiating the α- and γ-substituted isomers. The mass spectral fragmentation schemes are dominated by cleavages α to the carbonyl groups and by McLafferty rearrangements.

scholarly journals Synthesis and Pharmacological Evaluation of 2-(4-Halosubstituted phenyl)-4,5-diphenyl-1H-imidazoles

2008 ◽  
Vol 5 (3) ◽  
pp. 447-452 ◽  
Author(s):  
G. Nagalakshmi
Keyword(s):  
Anticonvulsant Activity ◽  
Glacial Acetic Acid ◽  
Ammonium Acetate ◽  
Antiinflammatory Activity ◽  
Aromatic Aldehydes ◽  
Mass Spectral Data ◽  
Mass Spectral ◽  
H Nmr ◽  
Structural Assignment ◽  
Paw Oedema

In the present study, 2-(4-halosubstituted phenyl)-4,5-diphenyl-1Himidazoles have been synthesized by refluxing benzil and ammonium acetate with different 4-halosubstituted aromatic aldehydes in glacial acetic acid. The structural assignment of this compound has been made on the basis of elemental analysis, UV, IR,1H NMR and Mass spectral data. Toxicity of the compound has been determined. The synthesized compound was evaluated for antiinflammatory activity against carrageenan induced paw oedema and anticonvulsant activity against maximal electro-shock-induced convulsions in rats.

A Chromone Based Fluorescent Probe for the Effective Detection of Aluminium Ion

2020 ◽  
Vol 20 (5) ◽  
pp. 2840-2846
Author(s):  
Hyorim Kim ◽  
Ramalingam Manivannan ◽  
Young-A Son
Keyword(s):  
Metal Ion ◽  
Color Change ◽  
Test Strip ◽  
Phenyl Hydrazine ◽  
Mass Spectral ◽  
H Nmr ◽  
Turn On ◽  
Molecular Charge ◽  
Intra Molecular Charge Transfer ◽  
Significant Interference

A new chromone moiety fused with phenyl hydrazine carboxamide as a binding site for metal ion was designed and synthesized as a colorimetric/fluorimetric probe for selective sensing of Al3+ ion. The absorption and fluorescence spectral results showed selective and sensitive recognition of Al3+ with no significant interference from other competitive metal ions. The addition of Al3+ to R brought a prompt color change from colorless to yellow and the turn-on fluorescence response with Al3+ among different cations was studied. The visible color change and turn-on fluorescence Al3+ ion with R was attributed to the intra molecular charge transfer transition. The plausible binding nature of the receptor with Al3+ has also been anticipated by the results of 1H NMR and mass spectral analysis. For the practical effectiveness, test strip prepared using probe R was successfully applied to monitor the presence of Al3+ ion in aqueous medium.

Sign in / Sign up

Export Citation Format

Share Document