Elsevier

Biochimie

Volume 92, Issue 9, September 2010, Pages 1164-1172
Biochimie

Research paper
Synthesis, Src kinase inhibitory and anticancer activities of 1-substituted 3-(N-alkyl-N-phenylamino)propane-2-ols

https://doi.org/10.1016/j.biochi.2010.04.022Get rights and content

Abstract

A series of 3-(N-alkyl-N-phenylamino)propan-2-ol derivatives were synthesized from epichlorohydrine in a multi-step strategy and were evaluated as Src kinase inhibitors. First, epoxy ring opening of epichlorohydrine was carried out in the presence of N-alkylanilines to yield 3-(N-alkyl-N-phenylamino)-1-chloro-propan-2-ol derivatives using Ca(OTf)2 as catalyst based on our previous studies [1]. Second, ring closure was performed under basic conditions to afford N-epoxymethyl N-alkylaniline derivatives. Finally, the epoxide ring opening with four different secondary amines and three nucleobases afforded the final products, i.e., a series of β-amino alcohols. All compounds were screened for their inhibitory activity against Src kinase and anticancer activity on human breast carcinoma cells, BT-20 cell line. Among all compounds, 3-N-methyl-N-phenylamino-1-(pyrrolidin-1-yl)propan-2-ol (13b) exhibited the highest inhibitory potency (IC50 = 66.1 μM) against Src kinase. Structure-activity relationship studies suggested that the incorporation of bulky groups at position 1 and N-substitution with groups larger than methyl moiety, reduced the inhibitory potency of the compound significantly. Compounds 3-(N-ethyl-N-phenylamino-)-1-(4-methylpiperazin-1-yl)propan-2-ol (14c) and 3-(N-ethyl-N-phenylamino)-1-(thymine-1-yl)propan-2-ol (17) were found to inhibit the growth of breast carcinoma cells by approximately 45–49% at concentration of 50 μM.

Introduction

Protein tyrosine kinases (PTKs) are enzymes responsible for the phosphorylation of other proteins and can catalyze the transfer of γ-phosphate group of ATP to the protein phenolic groups (on Tyr). PTKs play a central role in signal transduction pathways and are involved in immune, endocrine, and nervous system physiology and pathology. On the other hand, the abnormal phosphorylation could be a trigger of different diseases such as cancer [2]. PTKs are believed to be important in the development of many different types of cancers [3].

The Src family of PTKs is divided into 9 subfamilies, Src, Yes, Lck, Fyn, Lyn, Hck, Frg, Blk, and Yrk, based on catalytic domain sequence. Src kinases play crucial roles in signal transduction pathways and regulating various cellular functions such as cell proliferation and cell differentiation [4]. Src kinase is a protooncogenic tyrosine kinase [5] and has been implicated in the genesis and progression of multiple types of human cancer including colon, breast, lung, and other cancers [6].

Thus, designing Src kinase inhibitors is a subject of major interest by pharmaceutical industry. Most of the attention has been on designing Src kinase inhibitors through blocking Src-dependent phosphorylation of substrate proteins. The kinase domain inhibitors are designed to inhibit the binding of ATP (ATP-binding site inhibitors) [7], [7](a), [7](b) or the protein substrate (substrate binding site inhibitors) [8], [8](a), [8](b), [8](c). High affinity ligands targeting the ATP-binding site have been developed [9]. Unfortunately, most of the ATP-binding sites within protein kinases are highly conserved. This makes it very difficult to design a compound that inhibits a specific protein kinase by targeting the ATP-binding site.

Designing small-molecule inhibitors specific for the Src kinase domain is challenging due to the highly homologous nature of this domain within the Src family. Several experimental compounds [10], [10](a), [10](b), [10](c), such as PP1, PP2, CGP76030, SKI606, PD173955, PD180970, and SU6656 have been used for targeting the Src family of kinases. Only a few inhibitors have been tested without provoking toxicity in animal models [11]. Thus, there is opportunity to identify other small-molecule inhibitors or pharmacophore fragments that can inhibit Src kinase domain.

β-Amino alcohol fragment attracts interest as an important moiety present in vast range of biologically active natural and synthetic compounds [12], [12](a), [12](b), [12](c), [12](d), unnatural amino acids [13], [13](a), [13](b) and as chiral auxiliaries for asymmetric synthesis [14], [14](a), [14](b). Either the amine or the alcohol can be acylated, alkylated or contained within rings in β-amino alcohols. Compounds like bestatin [15], a syn-α-hydroxyl-β-amino acid belonging to this group is an aminopeptidase inhibitor that exhibits immunomodulatory activity [16], [16](a), [16](b) and is used as an adjuvant in cancer chemotherapy [17].

There are various anticancer drugs containing β-amino alcohol moiety as an important pharmacophore. Daunorubicin (1) and doxorubicin (2) are the two such examples that are known as potent and clinically useful agents in cancer chemotherapy. Daunorubicin and elsamicin A (3) contain vicinal amino alcohol moiety as sugar which is essential for their biological activity. Elsamicin A is an antitumor antibiotic in which the presence of amino sugar enhances the biological activity and the solubility of the antibiotic. Another example is bestatin (4) which contains a syn-α-hydroxy-β-amino acid (Fig. 1). Bestatin is an aminopeptidase inhibitor that exhibits immunomodulatory activity and is used clinically as an adjuvant in cancer chemotherapy [18], [18](a), [18](b), [18](c), [18](d).

There are certain form of cancers, cardiovascular and cerebrovascular diseases and ischemia/reperfusion injuries which are known to be caused by free radicals [19], [19](a), [19](b), [19](c), [19](d). Antioxidant prevent oxidative damage and protects body from the harmful effects of free radicals, a way to prevent cancer. In recent years diphenylalkyl piperazine derivatives containing the thio- or aminopropanol moiety have been evaluated for their calcium antagonistic and antioxidative activities [20]. Phenylamino and benzylamino derivatives of diphenylalkyl piperizine were found to possess inhibitory activity against auto-oxidative lipid peroxidations in canine brain homogenates [20]. 9-Substituted adenine and 1-substituted pyrimidine derivatives which incorporated the phenoxy-2-propanol moiety have also shown hypolipidimeic activity [21]. A number of nucleobase- and nucleoside-based drugs, like cytarabine, a chemotherapeutic agent used for the treatment of hematological malignancies such as acute myeloid leukemia, have also amino alcohol moiety.

Mukaiyama et.al. [22] reported the synthesis of potent pyrazolo[1,5-a]pyrimidine derivatives containing β-amino alcohols as Src kinase inhibitors. Lombardo et. al. [23], [23](a) and Das et. al. [23b] in Bristol-Myers Squibb Pharmaceutical research institute reported BMS-354825 (Dasatinib, trade name Sprycel), a 2-(aminopyrimidinyl)thiazol-5-carboxamides containing N-2-hydroxyethylpiperidine group, as a nanomolar Src/Abl kinase inhibitor.

Herein, we report the synthesis and evaluation of a series of 1-substituted 3-(N-alkyl-N-phenylamino)propane-2-ols as Src kinase inhibitors to establish the structural requirements surrounding the β-amino alcohols in small molecules for producing inhibitory potency. These compounds contain a nitrogen atom at the 3-position of propanol moiety. Furthermore, in some compounds β-amino alcohol moiety was combined with purine and pyrimidine nucleobases in one molecule. All synthesized compounds were also evaluated for their anticancer activity against human breast carcinoma cells.

Section snippets

Materials

Reactions were conducted under an atmosphere of nitrogen when anhydrous solvents were used. Column chromatography was carried out using silica gel (100–200 mesh). Analytical TLCs were performed on precoated Merck silica-gel 60F254 plates; the spots were detected under UV light. Silica gel (100–200 mesh) was used for column chromatography. Dry DMSO was kept over molecular sieves (4 Å) prior to use.

Physical measurements

Melting points were determined using H2SO4 bath and are uncorrected. The 1H NMR spectra were

Chemistry

The synthesis of 3-N-alkyl-N-phenylaminopropan-2-ol derivatives were achieved in three steps. In the first stage epoxy ring in epichlorohydrine (7) was opened with N-methylaniline (5) and N-ethylaniline (6) in the presence of freshly prepared calcium trifluoromethanesulfonate [Ca(OTf)2] to afford selectively 1-chloro-3-(N-methyl-N-phenylamino)propan-2-ol (8) and 1-chloro-3-(N-ethyl-N-phenylamino)propan-2-ol (5) in 80 and 87% yields, respectively, according to the previously reported procedure

Acknowledgements

We acknowledge the financial support from the National Medicinal Plant Board, New Delhi and American Cancer Society Grant # RSG-07-290-01-CDD. DS, RKS and SB thank University of Delhi, Department of Biotechnology and University Grant Commision (New Delhi, India) respectively, for the fellowships.

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