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Fluorenylmethoxycarbonyl-N-methylamino acids synthesized in a flow tube-in-tube reactor with a liquid-liquid semipermeable membrane

: Buba, Annette E.; Koch, Stefan; Kunz, Horst; Löwe, Holger


European Journal of Organic Chemistry 2013 (2013), Nr.21, S.4509-4513
ISSN: 1434-193X
ISSN: 1099-0690
Fraunhofer ICT-IMM ()
Amino acids; Flow chemistry; heterocyclic chemistry; microreactor; Oxazolid­inones

Both steps of the N-methylation of 9-fluorenylmethoxycarbonyl (Fmoc) amino acids were carried out in a microstructured tube-in-tube reactor equipped with a semipermeable Teflon® AF 2400 membrane as the inner tubing. In the first step, gaseous formaldehyde was passed through the inner membrane to effect the acid-catalyzed conversion of the Fmoc amino acids into the corresponding N-Fmoc oxazolidinones. In the second step, liquid–liquid transfer of trifluoroacetic acid was used for the first time in such a reactor for the reductive opening of these oxazolidinones to give Fmoc N-methylamino acids in high yields.