Brad Sleebs - Effective methods for the synthesis of N-methyl b-amino acids from all twenty common a-amino acids using 1,3-oxazolidin-5-ones and 1,3-oxazinan-6-ones

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  Publication Details (including relevant citation   information):

  Helvetica   Chimica Acta (2006),   89(11),   2611-2637

  Abstract:

  N-Methyl b-amino acids are generally required for application in   the synthesis of potentially bioactive

  modified peptides and other oligomers. Previous work highlighted   the reductive cleavage of 1,3-oxazolidin-

  5-ones to synthesise N-methyl a-amino acids. Starting from   a-amino acids, two approaches were

  used to prepare the corresponding N-methyl b-amino acids. First,   a-amino acids were converted to Nmethyl

  a-amino acids by the so-called 71,3-oxazolidin-5-one strategy8,   and these were then homologated

  by the Arndt–Eistert procedure to afford N-protected N-methyl   b-amino acids derived from the 20 common

  a-amino acids. These compounds were prepared in yields of 23–57%   (relative to N-methyl a-amino

  acid). In a second approach, twelve N-protected a-amino acids   could be directly homologated by the

  Arndt–Eistert procedure, and the resulting b-amino acids were   converted to the 1,3-oxazinan-6-ones in

  30–45% yield. Finally, reductive cleavage afforded the desired   N-methyl b-amino acids in 41 –63% yield.

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