A novel synthesis of (3R,4R)-4-acetoxy-3-[(R)-1-(t-butyldimethylsilyloxy)ethyl]-2-azetidinone, the versatile key intermediate of carbapenem synthesis, from (S)-ethyl lactate
作者:Yoshio Ito、Takeo Kawabata、Shiro Terashima
DOI:10.1016/s0040-4039(00)85317-4
日期:——
A highly efficient synthesis of the title compound was accomplished employing the addition of diketene to chiral imine as a key stereoselective reaction and using inexpensive ()-ethy1 lactate as a starting material.
Novel syntheses of the carbapenem key intermediates, (3R,4R)-4-acetoxy-3-[(R)-1-(t-butyldimethylsilyloxy)ethyl]-2-azetidinone and (3S,4R)-3-[(R)-1-(t-butyldimethylsilyloxy)ethyl]-4-carboxymethyl-2-azetidinone, from (S)-ethyl lactate
Two types of the carbapenem key intermediates (4 and 6) have been efficiently synthesized from inexpensive (S)-ethyllactate (7). Thus, (S)-2-benzyloxypropanal readily obtainable from 7 was condensed with di-p-anisylmethylamine to give the chiral imine. The [2+2]-cycloaddition reaction of diketene with the imine underwent in a highly stereoselective manner, yielding the desired 3,4-trans-3-acetyl-β-lactam