| 摘要 |
A process for preparing 4-substituted azetidinone derivatives of the formula: <IMAGE> wherein R is hydrogen or an easily removable protecting group; R1 is alkyl which can be substituted by hydroxy which can be protected or halogen; R2 is hydrogen or alkyl; R3 is alkyl, trialkylsilyl, phenyl which can be substituted by alkyl, alkoxy, nitro or halogen, cycloalkyl, naphthyl, anthracenyl, fluorenyl, benzothiazolyl or naphthalimidyl; and R4 is an electron withdrawing group or can form a ring together with R3, which comprises reacting an azetidinone derivative of the formula: <IMAGE> wherein R and R1 are as defined above, and Z is a leaving group, and an imide compound of the formula: <IMAGE> wherein R2, R3 and R4 are as defined above, in the presence of a titanium compound of the formula:Ti(Cl)n(OR5)mwherein R5 is lower alkyl, n and m are respectively an integer from 0 to 4, provided that n plus m always makes 4, and a base. The process of the present invention is an industrially advantageous process using a titinium compound which is inexpensive and easy to handle. 4-Substituted azetidinone compounds prepared according to the process of the present invention can be easily hydrolyzed to a carboxylic acid which is an important intermediate for the synthesis of carbapenem compounds.
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