Synthesis, Conformational Analysis and Transannular Reactions of 5,9-Propanobenzo[7]annulene Derivatives

1997 ◽  
Vol 62 (10) ◽  
pp. 1585-1598 ◽  
Author(s):  
Pelayo Camps ◽  
Diana Görbig ◽  
Victoria Muñoz-Torrero ◽  
Francesc Pérez
Keyword(s):  
Conformational Analysis ◽  
Molecular Mechanics ◽  
Related Compound ◽  
Methyl Derivative ◽  
Reaction Conditions ◽  
Molecular Mechanics Calculations ◽  
H Nmr ◽  
Nmr Data ◽  
Acid Catalyzed

(5α,9α,11β)-11-Hydroxy-6,7,8,9-tetrahydro-5H-5,9-propanobenzo[7]annulen-7-one ethylene ketal (6a) and its 11α-methyl derivative (6b) were prepared from monoketal 3. These compounds underwent acid-catalyzed transannular reactions leading to 6,7,8,9-tetrahydro-5H-5,9-propanobenzo[7]annulene derivatives 5a, 8a and 5b, 8b, respectively, depending on the reaction conditions. The compounds 6a and 6b were dehydrated to 6,7,8,9-tetrahydro-5H-5,9-prop[1]enobenzo[7]annulen-7-one (9a) and its 11-methyl derivative (9b), respectively. The conformational analysis of the 5,9-propanobenzo[7]annulene derivatives by molecular mechanics calculations (MM3 program) and the 1H NMR data show that hydroxyketal 6a and the related compound (5α,7β,9α)-6,7,8,9-tetrahydro-5H-5,9-propanobenzo[7]annulen-7-ol (4) exist mainly in the boat-chair conformation with the boat cycloheptenol ring, while for hydroxyketal 6b the chair-boat conformation (chair cycloheptenol ring) seems to be the preferred one.

Circular Dichroism and Conformational Analysis of Diastereomeric Bicamphors

2000 ◽  
Vol 65 (4) ◽  
pp. 477-489 ◽  
Author(s):  
Stefan E. Boiadjiev ◽  
David A. Lightner
Keyword(s):  
Nmr Spectroscopy ◽  
Conformational Analysis ◽  
Molecular Mechanics ◽  
Spectral Data ◽  
Relative Orientation ◽  
Nmr Analysis ◽  
Molecular Mechanics Calculations ◽  
H Nmr ◽  
The Third ◽  
Carbonyl Chromophores

Stereospecific syntheses afforded endo,endo- (1) and exo,exo- (2) bicamphors, while the third possible diastereomeric exo,endo-bicamphor (3) originated from nonselective camphor radical dimerization. The stereochemistry of bicamphor linkage was confirmed by 1H NMR analysis. Chiroptical and ultraviolet spectral data are presented for the three diastereomers 1-3 to show interchromophoric interaction. Conformational analysis to evaluate the relative orientation of each pair of carbonyl chromophores was accomplished by 1H NMR spectroscopy and molecular mechanics calculations.

scholarly journals Conformational Analysis in 18-Membered Macrolactones Based on Molecular Modeling

2011 ◽  
Vol 2011 ◽  
pp. 1-5 ◽  
Author(s):  
Salah Belaidi ◽  
Dalal Harkati
Keyword(s):  
Molecular Dynamics ◽  
Molecular Modeling ◽  
Conformational Analysis ◽  
Molecular Mechanics ◽  
Conformational Flexibility ◽  
Molecular Mechanics Calculations

Conformational analysis of 18-ring membered macrolactones has been carried out using molecular mechanics calculations and molecular dynamics. A high conformational flexibility of macrolactones was obtained, and an important stereoselectivity was observed for the complexed macrolides. For 18d macrolactone, which was presented by a most favored conformer with 20.1% without complex, it was populated with 50.1% in presence of Fe(CO)3.

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