Development of novel benzotriazines for drug discovery.

BACKGROUND: The synthesis of novel benzotriazine heterocycles was developed independently around the same time by Bischler, Bamberger and Arndt. Over the years, different groups have reported the synthesis of benzotriazine based compounds. OBJECTIVE: This literature review gives an update on recent benzotriazine compounds and their applications. CONCLUSION: The benzotriazine core has been used in various drug discovery projects including anticancer, anti-inflammatory and antimalarial programs. Recently, the benzotriazine core was used to develop selective kinase inhibitors targeting SRC, VEGFr2, BCR-ABL and BCR-ABL-T315I. Two benzotriazine based compounds, tirapazamine for the treatment of cancer and TG100801 for the treatment of age-related macular degeneration, have entered clinical trials.

Inhibitors of ABL and the ABL-T315I mutation.

Chronic myelogenous leukemia (CML) is a hematological stem cell disorder caused by increased and unregulated growth of myeloid cells in the bone marrow, and the accumulation of excessive white blood cells. Abelson tyrosine kinase (ABL) is a non-receptor tyrosine kinase involved in cell growth and proliferation and is usually under tight control. However, 95% of CML patients have the ABL gene from chromosome 9 fused with the breakpoint cluster (BCR) gene from chromosome 22, resulting in a short chromosome known as the Philadelphia chromosome. This Philadelphia chromosome is responsible for the production of BCR-ABL, a constitutively active tyrosine kinase that causes uncontrolled cellular proliferation. An ABL inhibitor, imatinib, was approved by the FDA for the treatment of CML, and is currently used as first line therapy. However, a high percentage of clinical relapse has been observed due to long term treatment with imatinib. A majority of these relapsed patients have several point mutations at and around the ATP binding pocket of the ABL kinase domain in BCR-ABL. In order to address the resistance of mutated BCR-ABL to imatinib, 2(nd) generation inhibitors such as dasatinib, and nilotinib were developed. These compounds were approved for the treatment of CML patients who are resistant to imatinib. All of the BCR-ABL mutants are inhibited by the 2(nd) generation inhibitors with the exception of the T315I mutant. Several 3(rd) generation inhibitors such as AP24534, VX-680 (MK-0457), PHA-739358, PPY-A, XL-228, SGX-70393, FTY720 and TG101113 are being developed to target the T315I mutation. The early results from these compounds are encouraging and it is anticipated that physicians will have additional drugs at their disposal for the treatment of patients with the mutated BCR-ABL-T315I. The success of these inhibitors has greater implication not only in CML, but also in other diseases driven by kinases where the mutated gatekeeper residue plays a major role.

Development of prodrug 4-chloro-3-(5-methyl-3-{[4-(2-pyrrolidin-1-ylethoxy)phenyl]amino}-1,2,4-benzotriazin-7-yl)phenyl benzoate (TG100801): a topically administered therapeutic candidate in clinical trials for the treatment of age-related macular degeneration.

Age-related macular degeneration (AMD) is one of the leading causes of loss of vision in the industrialized world. Attenuating the VEGF signal in the eye to treat AMD has been validated clinically. A large body of evidence suggests that inhibitors targeting the VEGFr pathway may be effective for the treatment of AMD. Recent studies using Src/YES knockout mice suggest that along with VEGF, Src and YES play a crucial role in vascular leak and might be useful in treating edema associated with AMD. Therefore, we have developed several potent benzotriazine inhibitors designed to target VEGFr2, Src, and YES. One of the most potent compounds is 4-chloro-3-{5-methyl-3-[4-(2-pyrrolidin-1-yl-ethoxy)phenylamino]benzo[1,2,4]triazin-7-yl}phenol ( 5), a dual inhibitor of both VEGFr2 and the Src family (Src and YES) kinases. Several ester analogues of 5 were prepared as prodrugs to improve the concentration of 5 at the back of the eye after topical administration. The thermal stability of these esters was studied, and it was found that benzoyl and substituted benzoyl esters of 5 showed good thermal stability. The hydrolysis rates of these prodrugs were studied to analyze their ability to undergo conversion to 5 in vivo so that appropriate concentrations of 5 are available in the back-of-the-eye tissues. From these studies, we identified 4-chloro-3-(5-methyl-3-{[4-(2-pyrrolidin-1-ylethoxy)phenyl]amino}-1,2,4-benzotriazin-7-yl)phenyl benzoate ( 12), a topically administered prodrug delivered as an eye drop that is readily converted to the active compound 5 in the eye. This topically delivered compound exhibited excellent ocular pharmacokinetics and poor systemic circulation and showed good efficacy in the laser induced choroidal neovascularization model. On the basis of its superior profile, compound 12 was advanced. It is currently in a clinical trial as a first in class, VEGFr2 targeting, topically applied compound for the treatment of AMD.

Type 2 intramolecular N-acylazo Diels-Alder reaction: regio- and stereoselective synthesis of bridgehead bicyclic 1,2-diazines.

The type 2 intramolecular N-acylazo Diels-Alder reaction provides a regio- and stereoselective synthesis of bicyclic 1,2-diazine systems. A new method for the generation of N-acylazo dienophiles with tetra-n-butylammonium periodate is reported. X-ray crystallographic analysis allowed the quantification of structural distortions of the nonplanar bridgehead olefin and lactam functionalities in 1,2-diazine cycloadducts 11 and 15. Caprolactams and enantholactams were formed by stereoselective bridgehead alkene reduction, a process that transfers stereochemistry from the bridgehead lactam nitrogen to the bridgehead carbon. The sequence of transformations offers a convenient route for the diastereoselective synthesis of medium-ring nitrogen heterocycles and 1,4-diamines.

Discovery of [7-(2,6-dichlorophenyl)-5-methylbenzo [1,2,4]triazin-3-yl]-[4-(2-pyrrolidin-1-ylethoxy)phenyl]amine--a potent, orally active Src kinase inhibitor with anti-tumor activity in preclinical assays.

We describe the identification of [7-(2,6-dichlorophenyl)-5-methylbenzo [1,2,4]triazin-3-yl]-[4-(2-pyrrolidin-1-ylethoxy)phenyl]amine (3), a potent, orally active Src inhibitor with desirable PK properties, demonstrated activity in human tumor cell lines and in animal models of tumor growth.

Dual function catalysts. Dehydrogenation and asymmetric intramolecular Diels-Alder cycloaddition of N-hydroxy formate esters and hydroxamic acids: evidence for a ruthenium-acylnitroso intermediate.

The chiral ruthenium salen complex, 13b, functions as an efficient catalyst for the sequential oxidation and asymmetric Diels-Alder cycloaddition of hydroxamic acids and N-hydroxy formate esters. This result provides evidence for the formation of a ruthenium-nitroso formate (acyl nitroso) intermediate. The Diels-Alder precursors are prepared from simple building blocks, and the cycloadducts, bridged oxazinolactams, can serve as useful intermediates in organic synthesis.

Type 2 intramolecular N-acylnitroso Diels-Alder reaction: scope and application to the synthesis of medium ring lactams.

Heteroatom variants of the type 2 intramolecular Diels-Alder reaction provide an efficient method for the preparation of bridged bicyclic heterocycles. The type 2 variant of the intramolecular N-acylnitroso Diels-Alder reaction is an effective method for the synthesis of bridged bicyclic oxazinolactams. Structural studies of the cycloadducts have allowed for quantification of the deformations of the bridgehead functionalities and provided a strategy for the stereoselective synthesis of substituted seven- and eight-membered ring lactams. Diastereoselective cycloadditions followed by cleavage of the oxazine ring afford azepin-2-ones or azocin-2-ones.

Type 2 intramolecular N-acylnitroso diels-alder reaction: stereoselective synthesis of bridged bicyclic oxazinolactams.

[reaction: see text] The type 2 intramolecular N-acylnitroso Diels-Alder reaction has been employed for the synthesis of substituted bridged bicyclic oxazinolactams. Upon oxidation of hydroxamic acid 6, a 3-benzylated oxazinolactam (7) was synthesized with complete diastereoselectivity. Elaboration of cycloadduct 7 liberated a cis-3,7-disubstituted azocin-2-one (9).