Tricyclic [1,2,4]triazine 1,4-dioxides as hypoxia selective cytotoxins

Abstract

A series of novel tricyclic triazine-di- N-oxides (TTOs) related to tirapazamine have been designed and prepared. A wide range of structural arrangements with cycloalkyl, oxygen-, and nitrogen-containing saturated rings fused to the triazine core, coupled with various side chains linked to either hemisphere, resulted in TTO analogues that displayed hypoxia-selective cytotoxicity in vitro. Optimal rates of hypoxic metabolism and tissue diffusion coefficients were achieved with fused cycloalkyl rings in combination with both the 3-aminoalkyl or 3-alkyl substituents linked to weakly basic soluble amines. The selection was further refined using pharmacokinetic/pharmacodynamic model predictions of the in vivo hypoxic potency (AUC req) and selectivity (HCD) with 12 TTO analogues predicted to be active in vivo, subject to the achievement of adequate plasma pharmacokinetics.

Figure 1

Figure 2

Figure 2a. Predicted Hypoxic Selectivity (HCD) and Potency (AUC_req) for BTOs. Legend for Table 2a: ●compounds predicted inactive; , active in vivo; , not tested due to structural similarity to actives; , not active in vivo. Data from Refs and . Figure 2b. Predicted Hypoxic Selectivity (HCD) and Potency (AUC_req) for TTOs. Legend for Table 2b: ● TTOs from Table 1; , TTOs from Table 2; , TTOs from Table 3.

Figure 2

Figure 2a. Predicted Hypoxic Selectivity (HCD) and Potency (AUC_req) for BTOs. Legend for Table 2a: ●compounds predicted inactive; , active in vivo; , not tested due to structural similarity to actives; , not active in vivo. Data from Refs and . Figure 2b. Predicted Hypoxic Selectivity (HCD) and Potency (AUC_req) for TTOs. Legend for Table 2b: ● TTOs from Table 1; , TTOs from Table 2; , TTOs from Table 3.

Scheme 1^a

^aReagents: (i) NH₂CN, HCl, Δ; then 30% NaOH, Δ; (ii) CH₃CO₃H, CH₃CO₂H; (iii) NaNO₂, CF₃CO₂H; (iv) DMF, POCl₃, Δ; (v) t-BuNO₂, CH₂I₂, CuI, THF, Δ; (vi) R₂CH₂CH₂NH₂, DME, Δ; (vii) Stille or Heck coupling; (viii) CF₃CO₃H, CF₃CO₂H, DCM.

Scheme 2^a

^aReagents: (i) Ac₂O, dioxane; (ii) KNO₃, H₂SO₄; (iii) 5 M HCl, Δ; (iv) NH₂CN, HCl, Δ; then 30% NaOH, Δ; (v) CH₃CO₃H, CH₃CO₂H; (vi) NaNO₂, CF₃CO₂H; (vii) DMF, POCl₃, Δ; (viii) RCH₂CH₂NH₂, DME, Δ; (ix) CF₃CO₃H, CF₃CO₂H, DCM.

Scheme 3^a

^aReagents: (i) cHNO₃; (ii) H₂, Pd/C, cHCl, EtOH; (iii) Ac₂O, dioxane; (iv) cHNO₃, CF₃CO₂H; (v) cHCl, EtOH, Δ; (vi) NH₂CN, HCl, Δ; then 30% NaOH, Δ; (vii) NaNO₂, CF₃CO₂H; (viii) DMF, POCl₃, Δ; (ix) RCH₂CH₂NH₂, DME, Δ; (x) CF₃CO₃H, CF₃CO₂H, DCM.

Scheme 4^a

^aReagents: (i) fHNO₃, H₂SO₄; (ii) H₂, Pd/C, cHCl, EtOH; (iii) Ac₂O, dioxane; (iv) KNO₃, H₂SO₄; (v) 5 M HCl, Δ; (vi) NH₂CN, HCl, Δ; then 30% NaOH, Δ; (vii) NaNO₂, CF₃CO₂H; (viii) DMF, POCl₃, Δ; (ix) RCH₂CH₂NH₂, DME, Δ; (x) CF₃CO₃H, CF₃CO₂H, DCM.

Scheme 5^a

^aReagents: (i) fHNO₃, cH₂SO₄; (ii) H₂, Pd/C, cHCl, EtOH; (iii) Ac₂O, dioxane; (iv) KNO₃, H₂SO₄; (v) 5 M HCl, Δ; (vi) NH₂CN, HCl, Δ; then 30% NaOH, Δ; (vii) NaNO₂, CF₃CO₂H; (viii) DMF, POCl₃, Δ; (ix) RCH₂CH₂NH₂, DME, Δ; (x) CF₃CO₃H, CF₃CO₂H, DCM.

Scheme 6^a

^aReagents: (i) AlCl₃, AcCl, DCM; (ii) NH₂OH·HCl, pyridine; then HCl, Ac₂O, HOAc; (iii) cHNO₃, HOAc; (iv) cHCl, EtOH, Δ; (v) NH₂CN, HCl, Δ; then 30% NaOH, Δ; (vi) NaNO₂, CF₃CO₂H; (vii) DMF, POCl₃, Δ; (viii) R₂CH₂CH₂NH₂, DME, Δ; (ix) CF₃CO₃H, CF₃CO₂H, DCM; (x) NaNO₂, cH₂SO₄; then H₃PO₂ (xi) H₂, PtO₂, THF, EtOH; (xii) Ac₂O, dioxane; (xiii) CH₃CO₃H, HOAc; (xiv) NaOMe, MeOH, Δ.

Scheme 7^a

^aReagents: (i) KNO₃, cH₂SO₄; (ii) H₂, Pd/C, aq. HCl, EtOAc/EtOH; (iii) Ac₂O, dioxane; (iv) Zn, HOAc, Δ; (v) AlCl₃, AcCl, DCM; (vi) NH₂OH·HCl, pyridine; then HCl, Ac₂O, HOAc; (vii) fHNO₃, HOAc; (viii) cHCl, EtOH, Δ; (ix) NH₂CN, HCl, Δ; then 30% NaOH, Δ; (x) NaNO₂, CF₃CO₂H; (xi) DMF, POCl₃, Δ; (xii) R₂CH₂CH₂NH₂, DME, Δ; (xiii) CF₃CO₃H, CF₃CO₂H, DCM.

Scheme 8^a

^aReagents: (i) MsCl, iPr₂Net, DCM; (ii) aq. NHMe₂, DMF, Δ; (iii) cHNO₃, CF₃CO₂H; (iv) H₂, Pd/C, aq. HCl, EtOAc/EtOH; (v) Ac₂O, Et₃N, DCM; (vi) fHNO₃, HOAc; (vii) HCl, EtOH, Δ; (viii) NH₂CN, HCl, Δ; then 30% NaOH, Δ; (ix) NaNO₂, CF₃CO₂H; (iv) H₂, Pd/C, aq. HCl, EtOAc/EtOH; (v) Ac₂O, Et₃N, DCM; (vi) fHNO₃, HOAc; (vii) HCl, EtOH, Δ; (viii) NH₂CN, HCl, Δ; then 30% NaOH, Δ; (ix) NaNO₂, CF₃CO₂H; (x) DMF, POCl₃, Δ; (xi) EtNH₂, DME, Δ; (xii) CF₃CO₃H, CF₃CO₂H, DCM; (xiii) KNO₃, cH₂SO₄; (xiv) EtNH₂·HCl, Et₃N, DMF, Δ; (xv) HCO₂H, Ac₂O, THF; then BH₃·DMS.

Scheme 9^a

^aReagents: (i) t-BuNO₂, CH₂I₂, CuI, THF, Δ; (ii) AllylOH, Pd(OAc)₂, nBu₄NBr, NaHCO₃, DMF, Δ; (iii) morpholine, MeOH; then NaCNBH₃, HOAc; (iv) CF₃CO₂H, CF₃CO₃H, DCM;

Scheme 10^a

^aReagents: (i)NaH, (EtO₂C)₂CH₂, Et₂O; (ii) NaOH, EtOH; (iii) xylene, Δ; (iv) BH₃·DMS, THF; (v) H₂, Pd/C, MeOH; (vi) Ac₂O, Et₃N, DCM; (vii) cHNO₃, CF₃CO₂H; (viii) 5 M HCl, MeOH, Δ; (ix) NH₂CN, HCl, Δ; then 30% NaOH, Δ; (x) TBDMSCl, iPr₂NEt, DMF; (xi) t-BuNO₂, CH₂I₂, CuI, THF, Δ; (xii) Et₄Sn, Pd(PPh₃)₄, DME, Δ; (xiii) 1 M HCl, MeOH, Δ; (xiv) CF₃CO₃H, DCM; (xv) MsCl, iPr₂NEt, DCM; then morpholine, DMF, Δ; (xvi) cHCl, dioxane, Δ.

Scheme 11^a

^aReagents: (i) AllylSnBu₃, Pd(PPh₃)₄, DME, Δ; (ii) 9-BBN, THF; then NaOAc, H₂O₂; (iii) MsCl, iPr₂NEt, DCM; then morpholine, DMF; (iv) 1 M HCl, MeOH; (v) CF₃CO₃H, CF₃CO₂H,DCM.

Scheme 12^a

^aReagents: (i) 50% aq. HCOCO₂H, cH₂SO₄, dioxane, Δ; (ii) H₂, Pd/C, MeOH, dioxane; (iii) cH₂SO₄, EtOH; (iv) LiAlH₄, THF; (v) Ac₂O, pyridine, DMAP, DCM; (vi) Cu(NO₃)₂·3H₂O, Ac₂O; (vii) Ac₂O, dioxane; (viii) cHNO₃, CF₃CO₂H; (ix)) 5 M HCl, MeOH, Δ; (x) NH₂CN, HCl, Δ; then 30% NaOH, Δ; (xi) t-BuNO₂, I₂, CuI, THF, Δ; (xii) dihydropyran, PPTS, DCM; (xiii) Et₄Sn, Pd(PPh₃)₄, DME, Δ; (xiv) MeSO₃H, MeOH; (xv) CF₃CO₂H, CF₃CO₃H, DCM; (xvi) MsCl, iPr₂NEt, DCM; then morpholine, DMF, Δ.

Scheme 13^a

^aReagents: (i) t-BuNO₂, CH₂I₂, CuI, THF, Δ; (ii) Allyl alcohol, Pd(OAc)₂, nBu₄NBr, NaHCO₃, DMF; (iii) morpholine, NaCNBH₃, MeOH, DMF; (iv) CF₃CO₃H, CF₃CO₂H, DCM; (v) Et₄Sn, Pd(PPh₃)₄, DME, Δ; (vi) NH₂CN, HCl, Δ; then 30% NaOH, Δ; (vii) NaNO₂, CF₃CO₂H; (viii) DMF, POCl₃, Δ.