Synthesis of isotopically labelled amino acids

An efficient approach to the enantioselective synthesis of a series of amino acids from either bromoacetyl bromide or glycine is described using a [2,3]‐sigmatropic rearrangement to establish the stereogenic centre at C‐2 under mild conditions. Protected allylglycine 5 is a valuable building block to several amino acids e.g. hydrolytic cleavage of the auxiliary in 5 followed by deprotection gave L ‐allylglycine in 92% yield whilst oxidative cleavage of the terminal alkene followed by deprotection gave L ‐aspartic acid in 67% yield over the 2 steps. Furthermore alkene 5 may be converted to hydroxy ester 8 which is an intermediate for the synthesis of various amino acids including L ‐lysine and L ‐proline. Since the enantiomer of sultam 1 is commercially available, the analogous D ‐amino acids may be synthesised. This chemistry is readily adapted for the incorporation of isotopic labels for example for the synthesis of [1,2‐ 13 C 2 , 15 N]‐ L ‐homoserine 14 . Copyright © 2007 John Wiley & Sons, Ltd.