Characterization of Cyclic N-Acyliminium Ions by Infrared Ion Spectroscopy

N‐Acyliminium ions are highly reactive intermediates that are important for creating CC‐bonds adjacent to nitrogen atoms. Here we report the characterization of cyclic N‐acyliminium ions in the gas phase, generated by collision induced dissociation tandem mass spectrometry followed by infrared ion spectroscopy using the FELIX infrared free electron laser. Comparison of DFT calculated spectra with the experimentally observed IR spectra provided valuable insights in the conformations of the N‐acyliminium ions.

Stereoselective asymmetric synthesis of (+)-sedamine and (+)-allosedamine

A convenient method for the generation of (+)-sedamine and (+)-allosedamine in high optical purity has been elaborated. The key steps are the highly stereoselective 1,2-nucleophilic addition to SAMP hydrazones allowing the installation of the stereogenic center at C2 and ring closing metathesis.

A Novel and Highly Regioselective Approach to 5-Methoxy-6-substituted-3-sulfonyl-δ-enlactams from 5-Methoxy-3-sulfonyl Glutarimide: Synthesis of cis-2-Substituted-3-piperidinols

A convenient method for the preparation of 5-methoxy-6-substituted-3-sulfonyl-delta-enlactams via regioselective nucleophilic addition to 5-methoxy-3-sulfonyl glutarimide is described. Formal syntheses of L-733,060, CP-99,994, and cassine are also reported.

Enantioselective allyltitanations and metathesis reactions. Application to the synthesis of piperidine alkaloids (+)-sedamine and (-)-prosophylline

An enantioselective synthesis of the piperidine alkaloids (+)-sedamine and (-)-prosophylline is reported. The synthesis of (+)-sedamine has been achieved in 12 steps with an overall yield of 20% from benzaldehyde, and (-)-prosophylline was obtained in 15 steps with an overall yield of 9.2%, starting from D-glyceraldehyde acetonide 14. The key steps are enantioselective allyltitanation reactions and ring-closing or cross-metathesis reactions.

Asymmetric syntheses of pipecolic acid and derivatives

Results in the field of asymmetric synthesis of pipecolic acid derivatives are reviewed. Three sections describe the asymmetric syntheses of the title compounds (i) from the chiral pool (alpha-amino acids or carbohydrates) (ii) using a chiral auxiliary either derived from terpenes, alpha-amino acids, tartaric acid, an amine or beta-amino alcohols (iii) by means of asymmetric catalysis.