Premium
Quaternary Chiral β 2,2 ‐Amino Acids with Pyridinium and Imidazolium Substituents
Author(s) -
Mata Lara,
Avenoza Alberto,
Busto Jesús H.,
Corzana Francisco,
Peregrina Jesús M.
Publication year - 2012
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201202096
Subject(s) - nucleophile , electrophile , chemistry , dihedral angle , pyridinium , enantiomer , nucleophilic substitution , enantiomeric excess , medicinal chemistry , enantioselective synthesis , stereochemistry , organic chemistry , catalysis , hydrogen bond , molecule
The reactions of cyclic sulfamidates as electrophiles with a variety of nitrogen‐containing aromatic heterocycle nucleophiles, such as pyridines, N ‐alkylimidazoles and N ‐methylbenzimidazol, was explored. In all cases, although the nucleophilic substitution reactions occurred on quaternary centres, elimination products were not detected. The inversion of configuration at this quaternary centre was determined by X‐ray diffraction analysis and the enantiomeric excess of the reactions was checked by chiral HPLC. This synthetic approach allowed us to obtain a new family of chiral charged β 2,2 ‐amino acids, including a new bisamino acid that incorporates an imidazolium salt as a cross‐linker. In this context, the treatment of these chiral imidazolium salts with Ag 2 O opens the way to new chiral N‐heterocyclic carbenes, which are important substrates in the fields of organometallic and organocatalytic chemistry. Additionally, we have done a thorough conformational analysis of these β‐amino acid derivatives, both in the solid state and in solution. The most important conformational feature of these acyclic systems is the rigidity of the N‐CH 2 ‐C‐N + dihedral angle, which is essentially due to the gauche effect.