An empirical model for stereochemical control in the cyclization of cyclopropanetricarboxylic acid esters

Article abstract of DOI:10.1246/bcsj.20190096

Here, we report an empirical model for diastereoselective cyclopropanation of fumarate/maleate diesters with chloroacetate, sulfonium ylide, or ammonium ylide. With symmetrical fumarate/maleate diesters, cyclopropanation was found to proceed with a high level of diastereoselectivity in favor of the chiral isomer. In contrast, production of the meso isomer was observed in 3848% diastereoselectivity when unsymmetrical fumarate/maleate was employed. An improved synthesis of (N-desmethy)dysibetaine CPa in both racemic and enantiomeri-cally pure forms was furthermore achieved. Configurational analysis by experimental and calculated ¹³C NMR data is also reported.