Zinc Tetrafluoroborate-Mediated Ring Expansion of trans-Aziridine-2-carboxylates to cis-2-Iminothiazolidines and cis-Thiazolidine-2-iminium Tetrafluoroborates and Evaluation of Antimicrobial Activity

Cis-2-iminothiazolidines and cis-thiazolidine-2-iminium tetrafluoroborates were successfully produced from trans-N-alkyl aziridine-2-carboxylates and phenyl/alkyl isothiocyanates mediated by zinc tetrafluoroborate in refluxing DCE. Reactions were performed via a complete regio- and stereoselective process to give the title iminothiazolidines and cis-thiazolidine-2-iminium salts in moderate to good yields (35 to 82%) with a wide substrate scope. In addition, the antibacterial activity evaluation of these compounds, as well as the minimum inhibitory concentration (MIC) determination, revealed that only four cis-thiazolidine-2-iminium salts showed growth inhibition against Bacillus cereus.

Straightforward synthesis of various chiral pyrimidines bearing a stereogenic center adjacent to the C-2 position, including C-terminal peptide isosteres

The present study describes an efficient access to enantioenriched pyrimidines' derivatives from readily available Boc-AA-NH₂ and β-enaminones. This strategy allows the synthesis of a large variety of chiral pyrimidines (18 examples) with good yields from the chiral pool. In the case of peptide isosteres, this procedure proved to be highly stereoretentive and paves the way to the construction of C-terminal modified peptidomimetics as illustrated in the synthesis of two original pyrimidines containing pseudo-dipeptides.

Dynamic Kinetic Resolution Processes Based on the Switchable Configurational Instability of Allenyl Copper Reagents

The configurational instability of allenyl copper reagents is unveiled. An experimental study highlights the crucial role of Li⁺ and of the reaction temperature in the control of the configurational stability of allenyl copper reagents. A judicious choice of the reaction conditions allows efficient dynamic kinetic resolution processes and gives a one-pot access to homopropargylic alcohols or amines bearing up to four contiguous defined stereogenic centers.