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Asymmetric Synthesis of 4,4-(Difluoro)glutamic Acid via Chiral Ni(II)-Complexes of Dehydroalanine Schiff Bases. Effect of the Chiral Ligands Structure on the Stereochemical Outcome.


ABSTRACT: Four differently substituted chiral Ni(II)-complexes of dehydroalanine Schiff base were prepared and reacted with BrCF2COOEt/Cu under the standard reaction conditions. The observed diastereoselectivity was found to depend on the degree and pattern of chlorine substitution for hydrogen in the structure of the dehydroalanine complexes. The unsubstituted complex gave the ratio of diastereomers (S)(2S)/(S)(2R) of 66/34. On the other hand, introduction of chlorine atoms in the strategic positions on the chiral ligands allowed to achieve a practically attractive diastereoselectivity of (?98.5/1.5). Diastereomerically pure major product was disassembled to prepare 9-fluorenylmethyloxycarbonyl (Fmoc) derivative of (S)-4,4-difluoroglutamic acid.

SUBMITTER: Tokairin Y 

PROVIDER: S-EPMC6988766 | biostudies-literature | 2020 Jan

REPOSITORIES: biostudies-literature

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Asymmetric Synthesis of 4,4-(Difluoro)glutamic Acid via Chiral Ni(II)-Complexes of Dehydroalanine Schiff Bases. Effect of the Chiral Ligands Structure on the Stereochemical Outcome.

Tokairin Yoshinori Y   Shigeno Yuhei Y   Han Jianlin J   Röschenthaler Gerd-Volker GV   Konno Hiroyuki H   Moriwaki Hiroki H   Soloshonok Vadim A VA  

ChemistryOpen 20200129 1


Four differently substituted chiral Ni(II)-complexes of dehydroalanine Schiff base were prepared and reacted with BrCF<sub>2</sub>COOEt/Cu under the standard reaction conditions. The observed diastereoselectivity was found to depend on the degree and pattern of chlorine substitution for hydrogen in the structure of the dehydroalanine complexes. The unsubstituted complex gave the ratio of diastereomers (<i>S</i>)(2<i>S</i>)/(<i>S</i>)(2<i>R</i>) of 66/34. On the other hand, introduction of chlori  ...[more]

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