Conformation of ring A in 3-oxotriterpenoids. Dipole moments and CD spectra

1986 ◽  
Vol 51 (3) ◽  
pp. 611-620 ◽  
Author(s):  
Jiří Klinot ◽  
Václav Všetečka ◽  
Eva Klinotová ◽  
Alois Vystrčil
Keyword(s):  
Dipole Moments ◽  
Cd Spectra ◽  
Boat Form ◽  
Methyl Derivatives

The A ring of 3-oxotriterpenoids allobetulone (I) and 3-xo-lupane-28-nitrile (IV) exists by about 40% in the boat form as derived from comparison of their dipole moments with those of 2α-methyl derivatives II, V (chair models) and 2β-methyl compounds III, VI (boat models). The same result was obtained from the CD spectra of 3-oxotriterpenoids I-VIII and from isomerization of the 2α- and 2β-substituted ketones XI and XII, respectively.

Preparation, spectral properties and biological activities of 5-bromo-6-methyl-2'-deoxyuridine and 5-iodo-6-methyl-2'-deoxyuridine

1980 ◽  
Vol 45 (8) ◽  
pp. 2364-2370 ◽  
Author(s):  
Antonín Holý ◽  
Erik De Clercq
Keyword(s):  
Antiviral Activity ◽  
Spectral Properties ◽  
De Novo ◽  
Biological Activities ◽  
Rabbit Kidney ◽  
Kidney Cells ◽  
Cd Spectra ◽  
Methyl Derivatives ◽  
Primary Rabbit

Reaction of 3',5'-di-O-benzoyl-6-methyl-2'-deoxyuridine (IIa) with elementary bromine or iodine afforded 5-halogeno derivatives IIc and IId which on methanolysis gave 5-bromo-6-methyl-2'-deoxyurine (Ic) and 5-iodo-6-methyl-2'-deoxyurine (Id), respectively. The CD spectra of Ic, Id and 6-methyl-2'-deoxyuridine (Ia) are compared and discussed with regard to determination of the nucleoside conformation. Unlike 5-bromo- and 5-iodo-2'-deoxyuridine, the 6-methyl derivatives Ic and Id exhibit neither antibacterial nor antiviral activity. Nor do they exert any antimetabolic effect on the de novo DNA synthesis in primary rabbit kidney cells.

Conformational states of methylamides of N-acetyl α-amino acids and their N-methyl derivatives III. Dipole moments

1973 ◽  
Vol 9 (3) ◽  
pp. 328-333
Author(s):  
E. S. Efremov ◽  
P. V. Kostetskii ◽  
V. T. Ivanov ◽  
E. M. Popov ◽  
Yu. A. Ovchinnikov
Keyword(s):  
Amino Acids ◽  
Dipole Moments ◽  
Conformational States ◽  
Methyl Derivatives

scholarly journals The Studies of Conditions for Inducing Chirality to Cu(II) Complexes by Chiral Zn(II) and Ni(II) Complexes with Schiff Base

2009 ◽  
Vol 2009 ◽  
pp. 1-4 ◽  
Author(s):  
Takashiro Akitsu ◽  
Jun Yamaguchi ◽  
Naoki Uchida ◽  
Yoshikazu Aritake
Keyword(s):  
Schiff Base ◽  
Hybrid Materials ◽  
Dipole Moments ◽  
Model Systems ◽  
Electron Conductivity ◽  
The Novel ◽  
Cd Spectra ◽  
Test Conditions ◽  
Methanol Solutions ◽  
Chiral Schiff Base

Recently, we have discovered that some chiral Schiff-base nickel(II) complexes induced d-d bands of CD spectra of some achiral copper(II) complexes. However, the novel phenomenon could be observed only a few systems of hybrid materials or limited conditions so far. In order to test conditions about copper(II) ions, we investigated model systems (1) metal-dendrimer (Cu-PAMAM; G4-NH2terminal) containing relatively small amount of copper(II) ions (4.5 equivalent to PAMAM) for modeling separated systems of achiral copper(II) complex from chiral Schiff-base nickel(II) or zinc(II) complexes, Bis(N-R-1-naphtylethyl-3,5-dichlorosalicydenaminato)nickel(II) or zinc(II) by polymer matrix. (2) equilibrium of copper(II)N-ethylethylenediamine complexes to measure absorption spectra of d-d band, pH, and electron conductivity during titration of copper(II) ions. The results showed that (1) 4.5Cu-PAMAM could not be induced their d-d bands by the chiral nickel(II) or zinc(II) complexes, which suggested that separation by polymers prevented from inducing CD peaks. (2) Although 36Cu-PAMAM was known, uncoordinated copper(II) ions excess to ligands mainly attributed to increase electron conductivity by remained ions in methanol solutions, which was not associated with intermolecular interaction or dipole moments being effective for the induced CD mechanism by using molecular recognition between neutral molecules of metal complexes.

Preparation of isomeric 2-methyl-1-oxotriterpenoids of the 18α-oleanane series; Conformation of ring A

1986 ◽  
Vol 51 (12) ◽  
pp. 2869-2878 ◽  
Author(s):  
Jiří Klinot ◽  
Jarmil Světlý ◽  
Eva Klinotová ◽  
Miloš Buděšínský ◽  
Alois Vystrčil
Keyword(s):  
Methyl Ketone ◽  
Selenium Dioxide ◽  
Allylic Oxidation ◽  
Hydroxy Derivative ◽  
Boat Conformation ◽  
H Nmr ◽  
Chloro Derivative ◽  
Alternative Approach ◽  
Boat Form ◽  
Methyl Derivatives

2β-Methyl-1α-hydroxy (XV) and two isomeric 2-methyl-1-oxo derivatives (XVI and XVII) of 19β,28-epoxy-18α-oleanane were prepared from 19β,28-epoxy-2-methyl-18α-olean-1-en-3-one (XI) via 3β-chloro derivative XIII and unsaturated 1α-hydroxy derivative XIV. Allylic oxidation of 2-methyl-2-ene VI was studied as an alternative approach to compound XIV. Oxidation with selenium dioxide led to diol VII, aldehyde VIII and alcohol IV, oxidation with tert-butyl chromate gave epoxy ketone X. According to 1H NMR and CD data, ring A in the 2β-methyl derivatives XV and XVI exists in a boat conformation. The 2α-methyl ketone XVII (chair form) is more stable than its 2β-epimer XVI (boat form): only 9 ± 3% of XVI exists at equilibrium. Conformation of ring A in the unsubstituted 1-ketone I and differences in stability of the boat form in 1,2- and 2,3-disubstituted triterpenoids are discussed.

Preparation and absolute configuration at C(22) of 21,26,27-trinor-5α-cholestan-25→22-olide derivatives

1985 ◽  
Vol 50 (4) ◽  
pp. 869-877 ◽  
Author(s):  
Vladimír Pouzar ◽  
Pavel Drašar ◽  
Ivan Černý ◽  
Miroslav Havel
Keyword(s):  
Absolute Configuration ◽  
Side Chain ◽  
Cd Spectra ◽  
Methyl Derivatives

Epimeric 21,26,27-trinor-5α-cholestan-25→22-olides (X and XVII), 21,26,27-trinor-5α-cholest-23-en-25→22-olides (XV and XXII), and their 23-methyl derivatives XVI and XXIII were prepared by lengthening the side chain in 5α-pregnan-21-al (I). On the basis of CD spectra and chemical correlations with 21,26,27-trinor-5α-cholestane-22,25-diols, the configuration 22S was ascribed to lactones X, XXII and XXIII whereas lactones XV, XVI and XVII were assigned the 22R configuration.

Magnetic anisotropies and relative aromaticities of pyrrole, pyrazole, imidazole and their N-methyl derivatives

1981 ◽  
Vol 34 (9) ◽  
pp. 1835 ◽  
Author(s):  
KE Calder ◽  
RL Calvert ◽  
PB Lukins ◽  
GLD Ritchie
Keyword(s):  
Magnetic Anisotropy ◽  
Dipole Moments ◽  
Effective Polarizability ◽  
Plane Component ◽  
Out Of Plane ◽  
Local Contribution ◽  
Non Local ◽  
Methyl Derivatives ◽  
Methyl Imidazole ◽  
Kerr Constants

Experimental dipole moments, molar Kerr constants and molar Cotton-Mouton constants at 298 K and 633 nm are reported for pyrrole, pyrazole, imidazole and their N-methyl derivatives as solutes in dioxan. Analysis of the Kerr-effect data yields the effective polarizability anisotropies which are used to evaluate the molecular magnetic anisotropies from the Cotton-Mouton constants. The magnetic criterion of aromaticity is applied by estimating for each molecule the non-local contribution to the out-of-plane component of the magnetizability and the magnetic anisotropy. Electron delocalization in these molecules is significantly less than that exhibited by benzene: pyrrole and N-methylpyrrole, c. 70%; pyrazole and N-methylpyrazole, c. 65%; imidazole and N-methyl-imidazole, c. 60%. Approximately one-third of the observed magnetic anisotropy arises from localized contributions.

Physical Properties of TCNQ Salts with N-Methyl Derivatives of Pyridine

1982 ◽  
Vol 85 (1) ◽  
pp. 257-263 ◽  
Author(s):  
A. Graja ◽  
M. Przybylski ◽  
B. Butka ◽  
R. Swietlik
Keyword(s):  
Physical Properties ◽  
Methyl Derivatives ◽  
Derivatives Of
Sign in / Sign up

Export Citation Format

Share Document