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.

Conformation of the A ring in 1-oxo and 3-oxotriterpenoids. Vicinal interproton coupling constants

1986 ◽  
Vol 51 (3) ◽  
pp. 593-610 ◽  
Author(s):  
Jiří Klinot ◽  
Miloš Buděšínský ◽  
Eva Klinotová ◽  
Alois Vystrčil
Keyword(s):  
Nmr Spectra ◽  
Chair Conformation ◽  
Spin Systems ◽  
Coupling Constants ◽  
Boat Conformation ◽  
H Nmr ◽  
Vicinal Coupling Constants ◽  
Full Analysis ◽  
Solvent Shifts ◽  
Methyl Derivatives

The coupling constants of the protons on the A ring were determined by full analysis of the spin systems in the 1H NMR spectra of 4,4-dimethyl-5α-cholestan-3-one (XIX) and 1-oxo and 3-oxo triterpenoids I, XIV-XVI, XX and their 2-methyl derivatives V, VI, XVII, XVIII, XXIII and XXIV. from the values of vicinal coupling constants it was inferred that in 2α-methyl-1-oxo and 3-oxo derivatives V, XVII and XXIII the A ring assumes a chair conformation, while in 2β-methyl derivatives VI, XVIII and XXIV a boat conformation. The chair form greatly predominates in 4,4-dimethyl-5α-cholestan-3-one (XIX) and in 1-oxotriterpenoid XX, while in triterpenoid 3-oxo derivatives I, XIV-XVI a significant amount of boat conformation is present at equilibrium (up to 40%). The solvent shifts and the lanthanide induced shifts of the protons on C(2) lead to the same conclusion.

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.

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.

A concise and efficient concurrent synthesis of 6,11-dihydrodibenzo[b,e]azepines and 5,6,11,12-tetrahydrodibenzo[b,f]azocines and their conversion to 4-oxo-8,13-dihydro-4H-benzo[5,6]azepino[3,2,1-ij]quinoline-5-carboxylates and N-acetyl-5,6,11,12-tetrahydrodibenzo[b,f]azocines: synthetic sequence, spectroscopic characterization and the structures of two products

2019 ◽  
Vol 75 (6) ◽  
pp. 650-656
Author(s):  
Lina M. Acosta Quintero ◽  
Alirio Palma ◽  
Justo Cobo ◽  
Christopher Glidewell
Keyword(s):  
Hydrogen Bonds ◽  
Three Dimensional ◽  
Spectroscopic Characterization ◽  
Boat Conformation ◽  
Framework Structure ◽  
Molar Ratios ◽  
Boat Form ◽  
Synthetic Sequence ◽  
Time Form ◽  
Twist Boat

Reaction of 2-allyl-N-benzyl-4-fluoroaniline or 2-allyl-N-benzyl-4-chloroaniline with 98% sulfuric acid leads to the concurrent formation of halogeno-substituted 11-ethyl-6,11-dihydrodibenzo[b,e]azepines, (II), and halogeno-substituted 11-methyl-5,6,11,12-tetrahydrodibenzo[b,f]azocines, (III), in each case in (II):(III) molar ratios of ca 2:1. Further reaction of (II) leads to ethyl 13-ethyl-2-halogeno-4-oxo-8,13-dihydro-4H-benzo[5,6]azepino[3,2,1-ij]quinoline-5-carboxylate, while acetylation of (III) gives the corresponding N-acetyl derivatives. The dibenzo[b,e]azepine and dibenzo[b,f]azocine ring systems are of importance in forming the core of a variety of bioactive compounds. In ethyl 13-ethyl-2-fluoro-4-oxo-8,13-dihydro-4H-benzo[5,6]azepino[3,2,1-ij]quinoline-5-carboxylate, C22H20FNO3, (IVa), the azepine ring adopts a conformation close to the twist-boat form, and the molecules are linked into a three-dimensional framework structure by a combination of C—H...O and C—H...π(arene) hydrogen bonds. The azocine ring in 5-acetyl-2-chloro-11-methyl-5,6,11,12-tetrahydrobenzo[b,f]azocine, C18H18ClNO, (Vb), adopts the boat–boat conformation and the molecules are again linked by C—H...O and C—H...π(arene) hydrogen bonds, but this time form a sheet structure.

The mechanism of allylic oxidation by selenium dioxide

1980 ◽  
pp. 706 ◽  
Author(s):  
Wolf-Dietrich Woggon ◽  
Felix Ruther ◽  
Huldrych Egli
Keyword(s):  
Selenium Dioxide ◽  
Allylic Oxidation

Conformational Study of N-Alkyl 5,6-Dihydro-7h,12h-Dibenz[C,F]Azocines by Nuclear Magnetic Resonance Spectroscopy

1975 ◽  
Vol 53 (2) ◽  
pp. 167-176 ◽  
Author(s):  
Robert R. Fraser ◽  
Mohammad A. Raza ◽  
Roger N. Renaud ◽  
Robert B. Layton
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Magnetic Resonance Spectroscopy ◽  
Resonance Spectroscopy ◽  
Boat Conformation ◽  
Conformational Study ◽  
Conformational Properties ◽  
Boat Form ◽  
Twist Boat ◽  
Influence Of Substituents

The influence of substituents on the conformational properties of N-substituted 5,6-dihydro-7H,12H-dibenz[c,f]azocines and their conjugate acids was studied by n.m.r. spectroscopy. The position of the equilibrium between a rigid boat-chair and a flexible twist-boat conformation has been measured. The twist-boat conformation in deuterochloroform increased as the size of the substituent increased. However, the effect was opposite for the series of conjugate acids in trifluoroacetic acid.A number of inversion barriers for the [Formula: see text] and the [Formula: see text] equilibria in CDCl3 and TFA were determined. It was found that all barriers to interconversion were raised on protonation. The barrier to racemization for the twist-boat form of the quaternary methiodide of 1 was found to be >18 kcal/mol.

Potential antidepressants: 2-(Phenylthio)aralkylamines

1989 ◽  
Vol 54 (7) ◽  
pp. 1995-2008 ◽  
Author(s):  
Jiří Jílek ◽  
Jiří Urban ◽  
Petr Taufmann ◽  
Jiří Holubek ◽  
Antonín Dlabač ◽  
...  
Keyword(s):  
Nmr Spectra ◽  
Benzyl Chloride ◽  
Lithium Aluminium Hydride ◽  
Pharmacological Profile ◽  
H Nmr ◽  
Lithium Aluminium ◽  
Alternative Approach ◽  
Phenyl Acetonitrile ◽  
Claisen Reaction ◽  
Pharmacological Testing

Reactions of 2-(phenylthio)benzyl chloride with dimethylamine, diethylamine, pyrrolidine, piperidine, morpholine, and 1-methylpiperazine afforded the title compounds VI-XI. Reaction of 2-(phenylthio)benzaldehyde with nitromethane gave the nitrostyrene XIV which was reduced with lithium aluminium hydride to 2-(2-(phenylthio)phenyl)ethylamine (XVI). This was transformed to the N-methyl and N,N-dimethyl derivatives XVIII and XIX. The Claisen reaction of (2-(phenylthio)phenyl)acetonitrile with ethyl acetate afforded compound XXI which was cleaved by phosphoric acid to (2-(phenylthio)phenyl)acetone (XX). The Leuckart-Wallach reaction afforded the formamide XXIII which was used as starting material for preparing the amines XXIV-XXVI. The alternative approach to these compounds starting by reaction of the aldehyde XII with nitroethane was complicated by the fact that in addition to the nitropropene XV 2-(phenylthio)benzonitrile was also formed. The synthetic use of the inhomogeneous XV resulted then in mixtures of amines XXIV-XXVI with IV-VI which was followed by means of mass and 1H NMR spectra. The amines XXIV-XXVI were oxidized to the sulfoxides XXVII-XXIX. The oily bases were transformed to crystalline salts and spectra of all homogeneous bases were recorded. Pharmacological testing showed the amine VI (VÚFB-15 370) to be a promising potential antidepressant. The amines XI and XXV showed also pharmacological profile of potential antidepressants.

Rhodium(I) complexes containing bidentate pyrazolylgallate ligands. X-ray crystal structures of [Me2Gapz2]Rh(COD), [Rh(μ-3,5-Me2pz)(CO)2]2, and [Rh(μ-3,5-Me2pz)(COD)]2

1984 ◽  
Vol 62 (6) ◽  
pp. 1057-1067 ◽  
Author(s):  
Brenda M. Louie ◽  
Steven J. Rettig ◽  
Alan Storr ◽  
James Trotter
Keyword(s):  
Solid State ◽  
Structural Parameters ◽  
Heavy Atom ◽  
Boat Conformation ◽  
Nmr Studies ◽  
Space Group ◽  
H Nmr ◽  
Square Planar ◽  
Dirhodium Complexes

The synthesis and characterization of the complexes [Me2Gapz2]Rh(LL) (where LL = COD, (CO)2, (PPh3)2, or (PPh3)(CO)), incorporating the bidentate, chelating, dimethylbis(1-pyrazolyl)gallate ligand are described. Non-rigidity in solution has been demonstrated by 1H nmr studies for some of the complexes. A crystal structure determination of the COD complex has confirmed the boat conformation for the Ga—(N—N)2—Rh six-membered ring in this complex in the solid state. In addition, the solid state structures of the 3,5-dimethylpyrazolyl bridged dirhodium complexes [Rh(μ-3,5-Me2pz)(CO)2]2 and [Rh(μ-3,5-Me2pz)(COD)]2 have been determined. Crystals of [Me2Gapz2]Rh(COD) are orthorhombic, a = 22.7447(8), b = 11.9776(5), c = 6.4635(3) Å, Z = 4, space group Pnma; those of [Rh(μ-3,5-Me2pz)(CO)2]2 are monoclinic, a = 8.7403(6), b = 16.3594(6), c = 25.434(2) Å, β = 95.286(3)°, Z = 8, space group P21/c; and those of [Rh(μ-3,5-Me2pz)(COD)]2 are triclinic, a = 10.350(2), b = 11.401(2), c = 12.355(2) Å, α = 112.485(7), β = 99.394(9), γ = 105.387(8)°, Z = 2, space group [Formula: see text]. All three structures were solved by conventional heavy atom techniques and were refined by full-matrix least-squares procedures to final conventional R values of 0.026, 0.024, and 0.037 for 1824, 5135, and 6109 reflections with I ≥ 3σ(I), respectively. In each case the Rh atoms have distorted square planar coordination geometry. Important mean structural parameters are Rh—N = 2.087(2), Rh—C = 2.129(2), [Formula: see text] for [Me2Gapz2]Rh(COD); Rh—N = 2.063(6), Rh—CO = 1.852(9), [Formula: see text] for [Rh(μ-3,5-Me2pz)(CO)2]2; and Rh—N = 2.084(1), Rh—C = 2.131(7), [Formula: see text] for [Rh(μ-3,5-Me2pz)(COD)]2.

Iseluxine: A Novel Isoquinolinone Alkaloid from Isei a luxurians§

2000 ◽  
Vol 55 (11-12) ◽  
pp. 1023-1025 ◽  
Author(s):  
Thomas Schimming ◽  
Kristina Jenett-Siems ◽  
Karsten Siems ◽  
Ludger Witte ◽  
Mahabir P. Gupta ◽  
...  
Keyword(s):  
Structural Elucidation ◽  
Missing Link ◽  
H Nmr ◽  
Methyl Derivatives ◽  
Derivatives Of ◽  
C Nmr

A novel isoquinolinone alkaloid, iseluxine (1), has been isolated from the epigeal parts of Iseia luxurians (Moric.) O’Donell (Convolvulaceae), a climber indigenous to the tropical Americas. Structural elucidation was achieved by HRM S, 1H NMR, 13C NMR , and HMBC spectroscopy. N- and / or O-m ethyl derivatives of 1 are already known from certain Magnoliidae families, e.g., the Fumariaceae, the Lauraceae, or the Papaveraceae. Iseluxine, the “missing link” in the biosynthesis of these methyl derivatives from dopamine, is the first isoquinolinone alkaloid characterized by a catechol substructure.

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