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Remarkable Diastereomeric Rearrangement of an α-Acyloxy β-Ketosulfide to an α-Acyloxy Thioester:  A Novel Approach to the Synthesis of Optically Active (2S,3S) β-Amino α-Hydroxy Acids

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journal contribution
posted on 02.09.2005 by Takayuki Suzuki, Yutaka Honda, Kunisuke Izawa, Robert M. Williams
A novel and efficient synthetic method is described for (2S,3S)-3-amino-2-hydroxy-4-phenyl butyric acid derivatives, which are useful intermediates of enzyme inhibitors. This involves a Pummerer rearrangement of a β-ketosulfoxide derived from l-phenylalanine followed by highly stereoselective acyl migration. From these studies, it appears that nitrogen-protecting groups exert a substantial influence over stereoselectivity. The mechanism of the rearrangement is discussed. β-Amino α-hydroxy carboxylic acids are important pharmaceutical intermediates, and this method may provide a versatile synthesis from various amino acids in a few steps.