N-Mono or N-disubstituted methyl-2-azetidinones are provided via cyclization of .beta.-hydroxy or .beta.-halo substituted acid sec-amides wherein the amide nitrogen is substituted with a mono- or di-substituted methyl group having activating substituents. Cyclization of .beta.-hydroxy acid amides is mediated by triphenylphosphine-dialkylazodicarboxylate while cyclization of .beta.-halo acid amides is mediated by strong bases e.g. lithium dialkylamides. E.g. Diethyl amino-protected L-serylaminomalonate is cyclized with 200 mole % TPP-diisopropylazodicarboxylate to N-(diethoxycarbonylmethyl)-3-protected-amino-2-azetidinone. The 2-azetidinones provided are useful intermediates.
通过环化β-羟基或β-卤代取代的酸辅酰胺制备N-单取代或N-二取代甲基-
2-氮杂环丁酮,其中酰胺氮原子被单取代或二取代甲基基团取代,具有活化取代基团。β-羟基酸酰胺的环化由
三苯基膦-二烷基偶氮二
羧酸酯介导,而β-卤基酸酰胺的环化由强碱介导,例如
锂二烷基胺。例如,
二乙基氨保护的
L-丝氨酸氨基丙二酸酯与200摩尔%
TPP-
二异丙基偶氮二
羧酸酯环化,形成N-(二乙氧羰基甲基)-3-保护
氨基-
2-氮杂环丁酮。提供的
2-氮杂环丁酮是有用的中间体。