Ready Available Chiral Azapyridinomacrocycles N-Oxides; First Results as Lewis Base Catalysts in Asymmetric Allylation of p-Nitrobenzaldehyde
摘要:
We report here the straightforward synthesis of the first series of enantiomerically pure azapyridinomacrocycles N-oxides containing a cyclohexyl chiral moiety. These compounds were readily obtained in good overall yields by a convergent synthesis using natural amino acids as starting building blocks and macrocyclisation as the key step. This method is rapid, efficient and suitable for the introduction of various substituents at the macrocyclic skeleton. Finally, the compounds were tested as organocatalysts for the enantioselective allylation of p-nitrobenzaldehyde with allyltrichlorosilane.
Ready Available Chiral Azapyridinomacrocycles N-Oxides; First Results as Lewis Base Catalysts in Asymmetric Allylation of p-Nitrobenzaldehyde
摘要:
We report here the straightforward synthesis of the first series of enantiomerically pure azapyridinomacrocycles N-oxides containing a cyclohexyl chiral moiety. These compounds were readily obtained in good overall yields by a convergent synthesis using natural amino acids as starting building blocks and macrocyclisation as the key step. This method is rapid, efficient and suitable for the introduction of various substituents at the macrocyclic skeleton. Finally, the compounds were tested as organocatalysts for the enantioselective allylation of p-nitrobenzaldehyde with allyltrichlorosilane.
Synthesis of an hexadentate tricyclic tetraazadiacetic ligand as precursor for MRI contrast enhancement agents
作者:Fabienne Dioury、Clotilde Ferroud、Alain Guy、Marc Port
DOI:10.1016/j.tet.2009.06.117
日期:2009.9
A tricyclic tetraazadiacetic compound, which is a rigidified derivative of cyclo-PCTA12 ligand with an oxo-ethylene bridge replacing an ethylene one, was prepared. The synthetic route involved the macrocyclization between an activated amido-disulfonamide and the 2,6-bis(bromomethyl)pyridine. The acetate side chains were grafted on the macrocyclic backbone to lead to the highly rigid tricyclic ligand in 34% overall yield in four steps from the linear amido-disulfonamide precursor. The corresponding Gd(III) and Mn(II) complexes were then prepared in order to evaluate their potential as contrast agent for MRI. (C) 2009 Elsevier Ltd. All rights reserved.