Lewis acid-promoted 1,4-addition to chiral imide derivatives in the synthesis of .beta.-amino acids
摘要:
The 1,4-addition of O-benzylhydroxylamine to imides 3 in the presence of various Lewis acids is described. The reaction is performed in CH2Cl2 at -78-degrees-C and affords derivatives 4 and 5 in good chemical yields and in different diastereomeric ratios, depending on the Lewis acid employed. TiCl4 and Me2AlCl give opposite diastereoselectivities. Furthermore, enantiomerically pure beta-amino acid 9 is obtained in good yield from compound 4a.