Reaction of N-Acyl-α-triphenylphosphonio-α-amino Acid Esters with Organic Bases: Mechanism of the Base-Catalyzed Nucleophilic Substitution of the Triphenylphosphonium Group |
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Authors: | Roman Mazurkiewicz Mirosława Grymel |
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Institution: | (1) Institute of Organic Chemistry and Technology, Silesian Technical University, PL-44100 Gliwice, Poland, PL |
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Abstract: | Summary. Reactions of N-acyl-α-triphenylphosphonio-α-amino acid methyl esters with organic bases (triethylamine or DBU) were investigated as the crucial step of the base-catalyzed displacement of the triphenylphosphonium group by nucleophiles.
It was proved that N-acyl-α-triphenylphosphonioglycinates are transformed to an equilibrium mixture of the corresponding N-acyliminoacetates and N-acyl-α-triphenylphosphoranylidene glycinates by bases. In the case of N-acyl-α-triphenylphosphonio-α-amino acid esters with quaternary α-carbon, the α-substituted homologues of the N-acyliminoacetates were detected to be the only primary reaction product which, however, can undergo further tautomerization
to the corresponding α,β-dehydro-α-amino acid derivatives. In both these cases the reaction of N-acyl-α-triphenylphosphonio-α-amino acid esters with nucleophiles proceeds via the addition of a nucleophile to the activated C=N double bond of the N-acylimino intermediate.
Corresponding author. E-mail: romanm@zeus.polsl.gliwice.pl
Received October 31, 2001. Accepted (revised) December 17, 2001 |
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Keywords: | ,N-α,-Triphenylphosphonioglycinates, Nucleophilic substitution, Synthetic equivalents of α,-amino acid α,-cations, Glycine,,,,,functionalization |
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