Addition of dimethyl phosphite to imines bearing the L‐methionine moiety and its surprisingly poor chiral assistance

The preparation of methyl 2‐{[(dimethoxyphosphoryl)‐methyl]‐amino}‐4‐methyl‐ sulfanylbutyrates ( 3a–e ) by the addition of dimethyl phosphite to 2‐(methylidenamino)‐4‐methylsulfanylbutyric acid methyl esters ( 2a–e ) is described. The nearly nonexisting diastereoselectivity, which was observed in all cases, is unexpected and astonishing in light of the fact that some other amino acid esters, e.g., leucine, demonstrated very high stereoselectivity in similar reactions. The separation of formed diastereoisomers occurred. © 2012 Wiley Periodicals, Inc. Heteroatom Chem 23:395–398, 2012; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.21029