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Enzymatic PMP Deprotection
J. M. M. Verkade, L. J. C. van Hemert, P. J. L. M. Quaedflieg, H. E. Schoemaker, M. Schürmann, F. L. van Delft, F. P. J. T. Rutjes*
Radboud University Nijmegen and DSM Pharmaceutical Products, Geleen, The Netherlands
23 August 2007 (online)
An enzymatic procedure for the oxidative deprotection of N-p-methoxyphenyl (PMP)-protected amines 1 (mostly benzylic amines) has been developed employing commercially available laccases T (from Trametes versicolor) or AB (from Agaricus bisporus). A phosphate buffer/acetonitrile mixture (4:1) at pH 3 was identified as optimal reaction medium and deprotected amines 2 could be obtained in reasonable to good yields. Higher amounts of cosolvent as well as a pH < 3 caused significantly decreased reaction rates. The use of ABTS as mediator (‘electron shuttle’) led to an extension of the substrate scope (see example 2a) and enhanced conversions in several cases. Moreover, concentration studies (up to 100 mg/mL) have been carried out to render the process industrially feasible. PMP-protected benzylamine (2b) furnished benzaldehyde rather than benzylamine under standard conditions.