4 research outputs found
Scale-up Synthesis of (<i>R</i>)- and (<i>S</i>)ā<i>N</i>ā(2-Benzoyl-4-chlorophenyl)-1-(3,4-dichlorobenzyl)pyrrolidine-2-carboxamide Hydrochloride, A Versatile Reagent for the Preparation of Tailor-Made Ī±- and Ī²āAmino Acids in an Enantiomerically Pure Form
Unusual amino acids
are of crucial importance to the synthesis
of bioactive peptides and new chemical entities. Innovative methodology
is always needed for the preparation of enantiomerically pure amino
acids that does not rely on tedious resolution procedures. The proline-derived
ligands (<i>R</i>)- and (<i>S</i>)-<i>N</i>-(2-benzoyl-4-chlorophenyl)-1-(3,4-dichlorobenzyl)Āpyrrolidine-2-carboxamide
are outstanding, versatile, and recyclable reagents for the synthesis
of tailor-made Ī±- and Ī²-amino acids. Here we report initial
studies of the scale-up synthesis of the HCl salt of these reagents
on the 100 g scale. The results demonstrate an increased efficiency
and environmental friendliness of the bench-scale procedure and provides
a firm foundation for the manufacture on multikilogram and larger
scales
Chemical Dynamic Thermodynamic Resolution and <i>S</i>/<i>R</i> Interconversion of Unprotected Unnatural Tailor-made Ī±āAmino Acids
Described
here is an advanced, general method for purely chemical
dynamic thermodynamic resolution and <i>S</i>/<i>R</i> interconversion of unprotected tailor-made Ī±-amino acids (Ī±-AAs)
through intermediate formation of the corresponding nickelĀ(II)-chelated
Schiff bases. The method features virtually complete stereochemical
outcome, broad substrate generality (35 examples), and operationally
convenient conditions allowing for large-scale preparation of the
target Ī±-AAs in enantiomerically pure form. Furthermore, the
new type of nonracemizable axially chiral ligands can be quantitatively
recycled and reused, rendering the whole process economically and
synthetically attractive
Chemical Dynamic Thermodynamic Resolution and <i>S</i>/<i>R</i> Interconversion of Unprotected Unnatural Tailor-made Ī±āAmino Acids
Described
here is an advanced, general method for purely chemical
dynamic thermodynamic resolution and <i>S</i>/<i>R</i> interconversion of unprotected tailor-made Ī±-amino acids (Ī±-AAs)
through intermediate formation of the corresponding nickelĀ(II)-chelated
Schiff bases. The method features virtually complete stereochemical
outcome, broad substrate generality (35 examples), and operationally
convenient conditions allowing for large-scale preparation of the
target Ī±-AAs in enantiomerically pure form. Furthermore, the
new type of nonracemizable axially chiral ligands can be quantitatively
recycled and reused, rendering the whole process economically and
synthetically attractive
Purely Chemical Approach for Preparation of dāĪ±-Amino Acids via (<i>S</i>)ātoā(<i>R</i>)āInterconversion of Unprotected Tailor-Made Ī±āAmino Acids
Unnatural (<i>R</i>)-Ī±-amino acids (Ī±-AAs)
are in growing demand in the biomedical research and pharmaceutical
industries. In this work, we present development of a purely chemical
approach for preparation of (<i>R</i>)-Ī±-AAs via (<i>S</i>)-to-(<i>R</i>)-interconversion of natural and
tailor-made (<i>S</i>)-Ī±-AAs. The method can be used
on free, unprotected Ī±-AAs and features a remarkable structural
generality including substrates bearing tertiary alkyl chains and
reactive functional groups. These attractive characteristics, combined
with simplicity of reaction conditions and virtually complete stereochemical
outcome, constitute a true methodological advance in this area, rivaling
previously reported chemical and biocatalytic approaches