Cyclization of the (4S)-PhCH2OCONHCH(CH2OH)CONHN=CH-aryl, obtained in 4 steps from L-serine, on
treatment with MeI and potassium carbonate, generates the chiral oxazolidinones, (4S)-N'-[(E)-(phenyl)methylidene]-Nmethyl-
2-oxo-1,3-oxazolidine-4-carbohydrazides. Overall the formation of the (4S)-N'-[(E)-(phenyl)methylidene]-Nmethyl-
2-oxo-1,3-oxazolidine-4-carbohydrazides from L-serine occurs with retention of configuration, as confirmed by Xray
crystallography. In contrast, the reaction of the N-Boc analogues, (4S)-t-BuOCONHCH(CH2OH)CONHN=CH-aryl,
on treatment with MeI / K2CO3, simply leads to N-methylation without cyclization and without loss of the Boc protecting
group to give (4S)-t-BuOCONMeCH(CH2OH)CONHN=CH-aryl. The difference between the Boc and Cbz derivatives is
striking and is probably linked to the greater bulk of the Boc group blocking the intramolecular acyl transfer.
Keywords: L-serine, N-Boc group, N-Cbz group, oxazolidinones, tuberculosis, X-ray crystallography.
Rights & PermissionsPrintExport