Asymmetric Induction in 8π Electrocyclizations. Design of a Removable Chiral Auxiliary
摘要:
The pseudo C-2 symmetric trans diphenyl oxazoline group acts as an effective chiral auxiliary in the 8 pi, 6 pi tandem electrocyclization of a substituted tetraene 1-carboxylic acid. Assignment of absolute stereochemistry to the [4.2.0] bicyclooctadiene product supports a model in which both s-cis and s-trans conformations favor the transition states with the same helical twist. This assignment prefaces the development of analogs of SNF4435 C and D. These natural products demonstrate activity as androgen receptor antagonists and as multidrug resistance (mdr) reversal agents.
Asymmetric Induction in 8π Electrocyclizations. Design of a Removable Chiral Auxiliary
摘要:
The pseudo C-2 symmetric trans diphenyl oxazoline group acts as an effective chiral auxiliary in the 8 pi, 6 pi tandem electrocyclization of a substituted tetraene 1-carboxylic acid. Assignment of absolute stereochemistry to the [4.2.0] bicyclooctadiene product supports a model in which both s-cis and s-trans conformations favor the transition states with the same helical twist. This assignment prefaces the development of analogs of SNF4435 C and D. These natural products demonstrate activity as androgen receptor antagonists and as multidrug resistance (mdr) reversal agents.
C−H Carbene Insertion of α-Diazo Acetamides by Photolysis in Non-Conventional Media
作者:Nuno R. Candeias、Pedro M. P. Gois、Luis F. Veiros、Carlos A. M. Afonso
DOI:10.1021/jo800980c
日期:2008.8.1
Light from a mercury vapor high-pressure lamp was used to induce the photolytic decomposition of alpha-diazo acetamides in hexane and in nonconventional media such as water or a film. The corresponding beta- and/or gamma-lactams were obtained in reasonable yields and in some cases with good diastereoselectivities with no need to use a metallic catalyst. Experimental studies on chiral substrates demonstrated the occurrence of insertion with retention of configuration.