Starting from (-)sclareol II, a natural product from Salvia sclarea, the Ambrox® I (an expensive flavouring and perfuming agent) has been constructed. The key reactions are: the formation of the lactone ring of sclareolide III based on the oxidative degradation of the side chain of sclareol and the reduction of the lactone ring to the furan ring of Ambrox® via the diol IV.
Cycloaddition of 2-diazopropane to an activated bicyclic ethylene. Photochemistry of the resulting Δ1-pyrazoline. The 1,3-dipolar cycloaddition of 2-diazopropane (DAP) to an activated symmetric ethylene 2 has enabled us to synthesise in good yield the Δ1-pyrazoline 3. When 3 was reacted with excess DAP, a symmetrical bis-Δ1-pyrazoline 4 was exclusively formed. The photolysis of the Δ1-pyrazoline 3 gives the expected cyclopropane derivative 5 quantitatively.
R. Gharbi, Z. Mighri, A. Khemiss
Reaction of the LDA and the Grignard reagents on the aliphatic N-2-cyano-2-methylvinyl and N-2-cyanophenylimidates provides aminopyridines and aminoquinolines respectively. In the absence of mobile hydrogen in a position with respect to the imidic carbon, the treatment of N-2-cyanophenyl-ethyl-benzimidate with organomagnesiums produces quinazolines.
M. Kamoun, B. Hajjem, H. Zantour, B. Baccar
Two new flavonoids were isolated from the medicinal plant Artemisia campestris, 3,5,3'-trihydroxy-7,4'-dimethoxy-6[3-methylbut-2-enyl]flavone (1) and 5-hydroxy-7,2',4',5'-tetramethoxy flavone (2). The structures were characterized by spectroscopic methods.
The aim of this work is the modelisation of the selectivity factor α versus the nature of the couple of solutes and the percentage of the organic modifier, on a column (Spherisorb ODS-2, 5 µm) and with a mobile phase acetonitrile/water or methanol/water varying between 40/60 and 80/20 in vol/vol. The nature of the couple of solutes is represented by the value of the logarithm of its selectivity factor α at 60% of organic modifier. This model allow the prediction of the mobile phase composition with which separation of solutes is possible.
F. Hellal, M. Debbabi
The crystal of CH3NH3CdBr3 exhibits an order disorder phase transition at 170 K from an hexagonal (Z = 2) to a complex orthorhombic (Z = 96) structure . A six dimensional pseudo spin model is tentatively used to describe the mechanism of this phase transition. Pseudo-spin coordinates, associated to the orientational disorder of the methylammonium groups in the hexagonal phase, are determined at different points of the Brillouin's zone. Coupling processes between these coordinates are able to provide possible solutions for the structure of the "projection" unit cell with Z = 12 , that could be taken as starting hypotheses for the structure determination of the complex unit cell of the low temperature phase.
A. Kallel, Y. Mlik
Review: Sclareol and its derivatives including Ambrox