Cyclopenta[g]quinazoline-based antifolates: the effect of the chirality at the 6-position on the inhibition of thymidylate synthase (TS)

Cyclopenta[g]quinazoline-based inhibitors of thymidylate synthase (TS) possess a chiral centre at the 6-position of the molecule. The effect of this chirality on the inhibition of TS was investigated by synthesising compounds 6S-1a-c, 6R-1a-c. It was shown, in particular with the diastereoisomers 6S-1c, 6R-1c, that the inhibitory activity against TS is mainly due to the 6S diastereoisomer rather than the 6R diastereoisomer, which is virtually inactive.

Synthesis of certain 2'-deoxyuridine derivatives containing substituted phenoxy groups attached to C-5'; evaluation as potential dUTP analogues

Derivatives of 2'-deoxyuridine in which the 5'-OH group is replaced by a 2,3,6-trifluoro-5-hydroxy-4-nitrophenoxy or a 4-carboxy-2,3,6-trifluoro-5-hydroxyphenoxy group have been prepared for evaluation as possible dUTP analogues. They showed a weak ability to displace radiolabelled dUTP from a dUTP-binding antiserum. The corresponding compounds lacking the three fluorine substituents were prepared for comparison.

Design and synthesis of Cyclopenta[g]quinazoline-based antifolates as inhibitors of thymidylate synthase and potential antitumor agents(,)

Following the development of raltitrexed, the synthesis of nonpolyglutamatable inhibitors of TS that do not use the reduced folate carrier (RFC) for cellular entry should provide compounds which overcome mechanisms of resistance to folate-based inhibitors of TS that are associated with decreased/altered folylpolyglutamate synthetase (FPGS) expression and/or an impaired RFC. Examination of a computer graphics model of the humanized Escherichia coli TS enzyme with quinazoline inhibitors of TS, such as 1 bound in the active site of the enzyme, suggested that conformational restriction introduced by bridging the C9 with C7 to form a pentacycle may be beneficial for binding to TS. That led to the synthesis of a series of potent cyclopenta[g]quinazoline-based inhibitors of the enzyme in which the glutamyl residue associated with classical antifolates was replaced with a variety of glutamate-derived ligands; the most potent inhibitor being the L-Glu-gamma-D-GluT(alpha) derivative 7j. In the mouse L1210:1565 cell line (mutant RFC), the majority of these compounds had activity equal or only slightly greater compared with the parental L1210 cell line, indicating a reduced dependence on the RFC for cellular uptake in the L1210 cell line.

Solid-phase synthesis of novel inhibitors of farnesyl transferase

A novel diphosphate mimic, the 2,3,6-trifluoro-5-hydroxy-4-nitrophenoxy group (1), has been employed as the template in the solid-phase synthesis of novel farnesyl transferase inhibitors using the Mitsunobu reaction. The most potent inhibitor (farnesyloxy-5-hydroxy-2,3,6-trifluoro-4-nitrobenzene) displayed an IC50 of 6.3 microM versus farnesyl transferase.

Folate-based inhibitors of thymidylate synthase: synthesis and antitumor activity of gamma-linked sterically hindered dipeptide analogues of 2-desamino-2-methyl-N10-propargyl-5,8-dideazafolic acid (ICI 198583)

In an effort to synthesize inhibitors of thymidylate synthase (TS) that do not undergo polyglutamation, a series of gamma-linked sterically hindered dipeptide analogues of 2-desamino-2-methyl-N10-propargyl-5,8-dideazafolic acid (ICI 198583) was prepared. A methyl, ethyl, or propargyl group was incorporated into the gamma-glutamyl amide bond of gamma-linked L,L dipeptide derivatives of ICI 198583, such as ICI 198583-gamma-L-Glu. In addition, steric bulk was introduced on either side of the gamma-glutamyl bond of ICI 198583-gamma-L-Glu or ICI 198583-gamma-L-Ala. The resulting dipeptide analogues, e.g., ICI 198583-gamma-MeGlu and ICI 198583-gamma-Aib, were apparently stable to in vivo hydrolysis but poorer inhibitors of TS and L1210 cell growth. However, introduction of 7-Me, 2'-F substitution into the quinazoline nucleus gave significant improvement in the inhibitory activity against thymidylate synthase. Compounds 28-30, the 7-Me, 2'-F derivatives of ICI 198583-gamma-MeGlu, ICI 198583-gamma-EtGlu, and ICI 198583-gamma-PgGlu, respectively, were potent inhibitors of TS (K(iapp) = 0.21-1.1 nM) and L1210 cell growth (IC50 = 0.05-0.34 microM) and were similar to that seen with the most potent gamma-linked L,D dipeptide derivatives of ICI 198583 previously synthesized. Furthermore, the low cross-resistance ratios for the L1210:R(D1694)/L1210 cell line indicated that 28-30 do not undergo polyglutamation.