Abstract:(S)-cyclohexylglycine (1) is prepared in high yield by hydrogenation of (S)-phenylglycine (2) using rhodium on carbon as the catalyst. Cyclohexylglycine (α-amino-cyclohexaneacetic acid) (1) is used as a nonnatural amino acid in pharmaceutical studies and in peptide chemistry. 1 Apart from its close analogy to phenylglycine (2), it functions as a structural mimic of the natural amino acids valine and isoleucine. 2 In connection with the synthesis of non-natural amino acids, we were looking for a method to prepa… Show more
“…This methodology is also available for other arylamino acids. In our hands, the basic method performed better than those with acidic conditions, and this approach is more amenable to scale-up as reactor compatibility problems with the acidic conditions are avoided. 3 …”
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confidence: 82%
“…3 Rhodium in the presence of acid has been used for the reduction of phenylglycine (vide infra). 4 Synthesis of L-cyclohexylalanine amide (3) is reported in a patent without any experimental detail. 2 L-Cyclohexylalaninol (2) 5 was prepared by the sodium or calcium borohydride reduction of the L-Boc-cyclohexylalanine methyl ester (6), 6 followed by hydrolysis of the Boc group (Scheme 1).…”
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confidence: 99%
“…Previous reported methods for the synthesis of l -cyclohexylalanine ( 1 ) involve the reduction of l -phenylalanine ( 4 ) using platinum oxide or platinum on carbon in acetic acid . Rhodium in the presence of acid has been used for the reduction of phenylglycine (vide infra) . Synthesis of l -cyclohexylalanine amide ( 3 ) is reported in a patent without any experimental detail…”
Catalytic reduction of phenylalanine and phenylglycine derivatives can be achieved with rhodium on carbon or alumina to give good yields of the corresponding cyclohexyl derivatives. The procedure can be scaled.
“…This methodology is also available for other arylamino acids. In our hands, the basic method performed better than those with acidic conditions, and this approach is more amenable to scale-up as reactor compatibility problems with the acidic conditions are avoided. 3 …”
mentioning
confidence: 82%
“…3 Rhodium in the presence of acid has been used for the reduction of phenylglycine (vide infra). 4 Synthesis of L-cyclohexylalanine amide (3) is reported in a patent without any experimental detail. 2 L-Cyclohexylalaninol (2) 5 was prepared by the sodium or calcium borohydride reduction of the L-Boc-cyclohexylalanine methyl ester (6), 6 followed by hydrolysis of the Boc group (Scheme 1).…”
mentioning
confidence: 99%
“…Previous reported methods for the synthesis of l -cyclohexylalanine ( 1 ) involve the reduction of l -phenylalanine ( 4 ) using platinum oxide or platinum on carbon in acetic acid . Rhodium in the presence of acid has been used for the reduction of phenylglycine (vide infra) . Synthesis of l -cyclohexylalanine amide ( 3 ) is reported in a patent without any experimental detail…”
Catalytic reduction of phenylalanine and phenylglycine derivatives can be achieved with rhodium on carbon or alumina to give good yields of the corresponding cyclohexyl derivatives. The procedure can be scaled.
“…Step one: chromatographic data acquisition for rac-9a-e. (i) Cbz N-protection, (ii) HCO 2 H, H 2 O, (iii) metal hydride reduction Inspection of the literature provided several examples of the selective and non-racemizing catalytic hydrogenation of a phenyl group in phenylglycine, phenylalanine or phenethylamine and analogues using ruthenium on carbon or rhodium on Al 2 O 3 (Sato et al 1998;Herlinger et al 1967;Strotmann and Butenschön 2000;Nugent 2002;Minnaard et al 1999;Hayashi et al 1983). These methods when applied to the hydrogenation of 3d on Rh/Al 2 O 3 or Ru/C catalyst gave quantitatively 3e.…”
Section: Scheme 5 Tandem Oxidation and Reduction To Recycle The Unresmentioning
The first successful resolution of rac-α-aminoacetals via diastereoisomeric salt formation with optically pure N-protected aminoacids is reported. The absolute configuration assignment of α-aminoacetal enantiomers is performed by an entirely non-racemizing chemical correlation method involving N-protection and a new efficient hydrolysis step followed by a reduction of the resulting N-protected α-aminoaldehyde intermediates. A racemization method of optically enriched α-aminoacetals is exemplified to allow valorisation of both enantiomers.
“…It involves a combination of organic synthesis for the preparation of the racemic α ‐amino amide followed by the use of a broadly specific α ‐amino amidase to achieve enantioselective resolution. In this work, the aryl group of l ‐( α Me)Phg was hydrogenated using 5% Rh/C as a catalyst (26). A quantitative conversion to l ‐( α Me)Chg was achieved at 59 °C and an H 2 pressure of 10 atm.…”
The novel Calpha-tetrasubstituted alpha-amino acid Calpha-methyl, Calpha-cyclohexylglycine was prepared by hydrogenation of its Calpha-methyl, Calpha-phenylglycine precursor. Terminally protected homodi-, homotri-, and homotetrapeptides from Calpha-methyl, Calpha-cyclohexylglycine and co-oligopeptides to the pentamer level in combination with Gly or alpha-aminoisobutyric acid residues were prepared by solution methods and fully characterized. The results of a conformational analysis, performed by use of Fourier transform infrared (FT-IR) spectrophotometer absorption, 1H NMR, and X-ray diffraction techniques, support the contention that this Calpha-methylated, Cbeta-trisubstituted aliphatic alpha-amino acid is an effective beta-turn and 3(10)-helix inducer in tri- and longer peptides as its Calpha-methyl valine parent compound, but partially divergent from the corresponding aromatic Calpha-methyl, Calpha-diphenylmethylglycine residue, known to promote folded and fully extended structures to a significant extent in these oligomers.
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