The 6,6-dibromopenam (6) was treated with CH3MgBr and carbaldehyde5 to afford the hydroxy compound7, which was reacted with acetic anhydride to give acetoxy compound8. The deacetobromination of8 with zinc and acetic acid gave 6-exomethylenepenams,E-isomer10 andZ-isomer9, which was oxidized to sulfone11 bym-CPBA. Thep-methoxybenzyl compounds were deprotected by AlCl3 and neutralized to give the sodium salts12, 13 and14.
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Im, C., Oh, J.S. & Yim, C.B. Synthesis of 6-exomethylenepenams as β-lactamase inhibitors. Arch Pharm Res 22, 68–71 (1999). https://doi.org/10.1007/BF02976438
- β-Lactamase Inhibitors