A Rapid Access to Both Enantiomers of 1,2,3,4-Tetranor B-Trienic 18,18,18-Trifluorosteroids. The First Enantiocontrolled Total Synthesis of 18,18,18-Trifluorosteroids
摘要:
Chiral A-tetranor B-trienic 18,18,18-trifluorosteroid 2a and its enantiomer 1a were synthesised by the thermolysis of chiral olefinic benzocyclobutenes 7b and 7a which were in turn prepared by the aldol reaction of chiral oxazolidinone 5 and 11 with 2-(4-methoxybenzocyclobutenyl-1)-acetaldehyde as a key step. The compound 1a was then transformed into 18,18,18-trifluorosteroid 9 via the ketone 13 and the diketone 14.
Michael addition reactions of a variety of Grignardreagents to 4,4,4-trifluorinated α,β-unsaturated carboxylic acid derivatives with the 4-substituted oxazolidin-2-ones as the chiral auxiliary were found to occur smoothly in the presence of CuBr·SMe2 and TMSCl to construct the desired products with the quaternary stereocenters possessing a CF3 group in good to excellent yields.
发现在CuBr·存在下,以4-取代的恶唑烷-2-酮为手性助剂的各种格氏试剂对4,4,4-三氟代α,β-不饱和羧酸衍生物的迈克尔加成反应均能顺利进行。 SMe 2和TMSC1以具有良好至优异产率的具有CF 3基团的四级立体中心构建所需产物。
A Rapid Access to Both Enantiomers of 1,2,3,4-Tetranor B-Trienic 18,18,18-Trifluorosteroids. The First Enantiocontrolled Total Synthesis of 18,18,18-Trifluorosteroids
Chiral A-tetranor B-trienic 18,18,18-trifluorosteroid 2a and its enantiomer 1a were synthesised by the thermolysis of chiral olefinic benzocyclobutenes 7b and 7a which were in turn prepared by the aldol reaction of chiral oxazolidinone 5 and 11 with 2-(4-methoxybenzocyclobutenyl-1)-acetaldehyde as a key step. The compound 1a was then transformed into 18,18,18-trifluorosteroid 9 via the ketone 13 and the diketone 14.