Potential Antitumor ${\alpha}$-methylene-${\gamma}$-butyrolactone-bearing nucleic acid bases. 2. synthesis of $5^I-Methyl-5^I$-[2-(5-substituted uracil-1-yl)ethyl]-$2^I-oxo-3^I$-methylenetetrahydrofurans

Ten, heretofore unreported, $ 5^I-methyl-5^I-[2-(5-substituted uracil-1-yl)ethyl)]-2^I-oxo-3^I$-methylenetetrahydrofurans (H, F, Cl, Br, I, $ CH_3$,$CF_3$,$CH_2CH_3$,$ CH=CH2$, SePh) (7a-j) were synthesized and evaluated against four cell lines (K-562, FM-3A, P-388 and U-937). For the preparation of ${\alpha}$-methylene-${\gamma}$-butyrolactone-linked to 5-substituted uracils (7a-j), the convenient Reformasky type reaction was employed which involves the treatment of ethyl ${\alpha}$-(bromomethyl)acrylate and zinc with the respective 1-(5-substituted uracil-1-yl)-3-butanone (6a-j). The 5-substituted uracil ketones (6a-j) were directly obtained by the respective Michael type reaction of vinyl methyl ketone with the $K_2CO_3$(or NaH)-treated 5-substituted uracils (5a-j) in the presence of acetic acid in the DMF solvent. The .alpha.-methylene-.gamma.-butyrolactone compounds showing the most significant antitumor activity are 7e, 7f, 7h and 7j (inhibitory concentration $(IC_50)$ ranging from 0.69 to $2.9 {\mu}g/ml$), while 7b, 7g and 7i have shown moderate to significant activity. The compounds 7a, 7c and 7d were found to be inactive. The synthetic intermediate compounds 6a-j were also screened and found marginal to moderate activity where compounds 6b and 6g showed significant activity $(IC_50:0.4~2.8 {\mu}g/ml)$.