Synthesis and In Vitro Antitumor Activity of Thiophene Analogues of 5-Chloro-5,8-dideazafolic Acid and 2-Methyl-2-desamino-5-chloro-5,8-dideazafolic Acid Original Research Article

N-[5-[N-(2-Amino-5-chloro-3,4-dihydro-4-oxoquinazolin-6-yl)methylamino]-2-thenoyl]-l-glutamic acid () and N-[5-[N-(5-chloro-3,4-dihydro-2-methyl-4-oxoquinazolin-6-yl)methylamino]-2-thenoyl]-l-glutamic acid (), the first reported thiophene analogues of 5-chloro-5,8-dideazafolic acid, were synthesized and tested as inhibitors of tumor cell growth in culture. 4-Chloro-5-methylisatin () was converted stepwise to methyl 2-amino-5-methyl-6-chlorobenzoate (22) and 2-amino-5-chloro-3,4-dihydro-6-methyl-4-oxoquinazoline (). Pivaloylation of the 2-amino group, followed by NBS bromination, condensation with di-tert-butyl N-(5-amino-2-thenoyl)-l-glutamate (), and stepwise cleavage of the protecting groups with ammonia and TFA yielded . Treatment of 9 with acetic anhydride afforded 2,6-dimethyl-5-chlorobenz[1,3-d]oxazin-4-one (), which on reaction with ammonia, NaOH was converted to 2,6-dimethyl-5-chloro-3,4-dihydroquinazolin-4-one (). Bromination of , followed by condensation with and ester cleavage with TFA, yielded . The IC50 of and against CCRF-CEM human leukemic lymphoblasts was 1.8±0.1 and 2.1±0.8 μM, respectively.