- Synthesis of Nonproteinogenic (R)- or (S)-Amino Acids. - Analogues of Phenylalanine, Isotopically Labelled and Cyclic Amino Acids from tert-Butyl 2-(tert-Butyl)-3-methyl-4-oxo-1-imidazolidinecarboxylate (Boc-BMI)
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The enantiomerically pure glycine derivatives (R)- and (S)-Boc-BMI, commercially available on a kg scale, are used as starting materials (Scheme 1) for the preparation of (i) open-chain amino acids such as α-deuterio amino acids (4,5), β-arylalanines (2), aspartic acid derivatives (6, 7a, 8), or ω-halo amino acids (7b,c, 12, 13, 16, 17, 19, 22), (ii) of α-aminocycloalkanecarboxylic acids (9, 11), and (iii) of heterocyclic α-amino acids (14, 15, 18, 20) containing azetidine, pyrrolidine, piperidine or perhydroazepine rings.Inversion by deprotonation/protonation ordeuteration allows to prepare either enantiomer of an amino acid from the same Boc-BMI enantiomer (Scheme 5).Effects of additives such as the cyclic urea DMPU, lithium salts, or secondeary amines upon the reactivity of lithium enolates are discussed and, in part, exploited.
- Seebach, Dieter,Dziadulewicz, Edward,Behrendt, Linda,Cantoreggi, Sergio,Fitzi, Robert
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p. 1215 - 1232
(2007/10/02)
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