Acetomycin

Acetomycin has antitumor activity in vitro but not in vivo. HCT-8 human colon adenocarcinoma assays in the presence of a drug metabolizing system (rat liver S9 fraction) demonstrated that liver enzymes inactivated acetomycin. The structure of acetomycin suggested that an esterase could be the key inactivating enzyme. Assays with porcine liver esterase (EC 3.1.1.1) showed that this enzyme rapidly abolishes the activity of acetomycin against HCT-8 cells. The potential utility of acetomycin as an antitumor agent thus depends on finding a means of preventing esterase inactivation.

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.

C10H14O5, Mr = 214.22, orthorhombic, P2(1)2(1)2(1), a = 14.1084 (6), b = 10.6443 (3), c = 7.1970 (1) A, V = 1080.80 (6) A3, Z = 4, D chi = 1.317 Mg m-3, Cu K alpha, lambda = 1.5418 A, mu = 0.8571 mm-1, F(000) = 456, T = 293 K, R = 0.052 for 816 observed [3 sigma (I)] Friedel pairs. The determined absolute configuration may be described as 3S, 4R, 5R, the five-membered ring having an envelope conformation, with the bulky substituents at cis positions. The bond lengths and angles are in agreement with those of the bromoacetoxy derivative.