RESUMO
[reaction: see text] An enantioselective synthesis of the chiral bisnaphthopyrone natural product nigerone is reported. The key step was an eight-step isomerization process to form the final natural product. The isomerization precursor was constructed via asymmetric oxidative biaryl coupling of an advanced intermediate with a 1,5-diaza-cis-decalin copper catalyst.
Assuntos
Produtos Biológicos/síntese química , Naftalenos/síntese química , Compostos Bicíclicos com Pontes/química , Catálise , Cobre/química , Compostos Heterocíclicos com 2 Anéis/química , Isomerismo , Modelos Químicos , Naftalenos/química , Oxirredução , Piperidinas/química , Pironas/síntese química , Pironas/químicaRESUMO
By using oxygen as the terminal oxidant, copper complexes derived from chiral 1,5-diaza-cis-decalin catalyze the enantioselective oxidative biaryl coupling of highly functionalized naphthols to provide octa- and decasubstituted binaphthalenes with high selectivity (86-90% ee). Products containing very electron-rich naphthalenes were prone to epimerization under the reaction conditions. This epimerization could be suppressed by employing naphthol starting materials with phenol protecting groups that attenuated the electron-rich nature of the naphthalenes. Direct oxidation of the resultant chiral 1,1'-binaphthol framework completed the first asymmetric synthesis of a perylenequinone containing only an axial chirality element.
