Design, Synthesis and Bioactivity Evaluation of 4,6-Disubstituted Pyrido[3,2- d]pyrimidine Derivatives as Mnk and HDAC Inhibitors

Abstract

Both HDACs and Mnks play important role in translating multiple oncogenic signaling pathways during oncogenesis. As HDAC and Mnk are highly expressed in a variety of tumors; thus simultaneous inhibit HDAC and Mnk can increase the inhibition of tumor cell proliferation and provide a new way of inhibiting tumor growth. Based on the previous work and the merge pharmacophore method; we designed and synthesized a series of 4,6-disubstituted pyrido[3,2-d]pyrimidine derivatives as HDAC and Mnk dual inhibitors. Among them; compound A12 displayed good HDAC and Mnk inhibitory activity. In vitro antiproliferative assay; compound A12 exhibited the best antiproliferative activity against human prostate cancer PC-3 cells. Docking study revealed that the pyrido[3,2-d]pyrimidine framework and hydroxamic acid motif of compound A12 were essential for maintaining the activity of HDAC and Mnk. These result indicated that A12 was a potent Mnk /HDAC inhibitor and will be further researched.

Keywords: HDAC and Mnk inhibitor; antiproliferative activity; pyrido[3,2-d]pyrimidine derivatives.

Figure 1

Representative HDAC inhibitors, dual HDAC/kinase inhibitors and Mnk inhibitors.

Figure 2

The interaction between HDAC and Mnk in tumor cells.

Figure 3

The structure of compound D06 and predicted binding mode of D06 with Mnk2.

Figure 4

Design strategy of dual HDAC/Mnk inhibitors.

Scheme 1

Synthesis of A01 and A07. Reagents and conditions: (a) SnCl₂·2H₂O, EtOH, reflux, 2 h; (b) CH(OCH₃)₃, 140 °C, 4 h; (c) POCl₃, N,N-dimethylaniline, reflux, 3 h; (d) 4-fluoroaniline, isopropanol, Et₃N, 50 °C, 0.5 h; (e) 4-carboxybenzeneboronic acid, Pd(dppf)Cl₂, K₂CO₃, 1,4-dioxane/H₂O, 90 °C, 3 h; (f) o-phenylenediamine, HATU, DMAP, DIPEA, THF, r.t., 2 h; (g) MeOH, H₂SO₄, reflux, 4 h; (h) NH₂OH·H₂O, NaOH, MeOH, 0 °C to r.t, 2 h.

Scheme 2

Synthesis of A02 and A08. Reagents and conditions: (a) malonate, pyridine, dry toluene, reflux, 2 h; (b) Pd(dppf)Cl₂, K₂CO₃, 1,4-dioxane/H₂O, N₂, 90 °C, 2 h; (c) o-phenylenediamine, HATU, DMAP, DIEA, DMF, r.t., 2 h; (d) MeOH, H₂SO₄, reflux, 4 h; (e) NH₂OH·H₂O, NaOH, MeOH, 0 °C to r.t., 2 h.

Scheme 3

Synthesis of A03 and A09. Reagents and conditions: (a) methyl 4-hydroxymethylbenzoate, CuI, 8-hydroxyquinoline, Cs₂CO₃, dry DMF, N₂, 90 °C, 2 h; (b) NH₂OH·H₂O, NaOH, MeOH, 0 °C to r.t., 2 h; (c) NaOH, DMF, 60 °C, 4 h; (d) o-phenylenediamine, HATU, DIPEA, DMAP, THF, r.t., 3 h.

Scheme 4

Synthesis of A04–A06 and A10–A19. Reagents and conditions: (a) Required amine, DIEA, DMF, 60 °C, 3 h; (b) SnCl₂·2H₂O, EtOH, reflux, 2 h; (c) CH(OCH₂CH₃)₃, 140 °C, 4 h; (d) POCl₃, N,N-dimethylaniline, 106 °C, 2 h; (e) required aniline, Pd₂(dba)₃, RuPhos, K₂CO₃, 1,4-dioxane, N₂, 90 °C, 2 h; (f) NH₂OH·H₂O, MeOH, NaOH, 0 °C to r.t., 2 h; (g) NaOH, DMF, 60 °C, 4 h; (h) o-phenylenediamine, HATU, DIPEA, DMAP, THF, r.t.,2 h.

Figure 5

The predicted binding mode of compound A12 with Mnk2(2hw7, A and B, binding energy: −177.95 kcal/mol) and HDAC1(1c3s, C and D, binding energy: −238.47 kcal/mol). The hydrogen bond interaction are colored in green.