Total synthesis of (+/-)-acetomycin and design of esterase-resistant analogs.

The synthesis of acetomycin and related analogs was investigated. Acetomycin was synthesized from diethyl allyl(methyl)malonate in 6.5% yield over 18 steps. The total number of steps was improved compared to our previous synthesis; i.e., four steps shorter, and the total yield was 4.5% greater than the previous synthesis. Acetomycin analogs with benzoyloxy and pivaloyloxy groups, instead of an acetoxy group at the 5-position of the gamma-butyrolactone ring were designed as esterase-resistant models and prepared similarly. Although they showed a similar level of cytotoxicity as acetomycin in vitro, they were not resistant to porcine liver esterase, and lost cytotoxicity in vivo.