Design, Synthesis, and Biologic Evaluation of Tetrahydroisoquinoline-Based CXCR4 Modulators Open Access

Truax, Valarie (2014)

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CXCR4 is a G-protein coupled receptor (GPCR) that binds to the chemokine, CXCL12 (SDF-1, stromal cell derived factor -1). The CXCR4/CXCL12 signaling axis plays an essential role during embryogenesis as well as mediating immune cell trafficking and stem cell homing to the bone marrow. Dysregulation of the CXCR4/CXCL12 axis is also linked to several pathological conditions; including X4-tropic HIV-1 infection, cancer metastasis and inflammation. In an effort to discover potential treatments for these disorders, enormous efforts have been made by the research community to understand the mechanisms that govern CXCR4 signaling and develop novel and effective CXCR4 modulators.

In Chapter 2, the synthesis and structure activity relationship of novel AMD3100, 1,4-bis((1,4,8,11-tetraazacyclotetradecan-1-yl)methyl)benzene analogs are presented. These compounds have been evaluated for CXCR4 mediated effects in the viral attachment assay with HIV-1III-B in CCR5/CXCR4-expressing HeLa-CD4-LTR-β-gal (MAGI) cells measuring each compound's ability to block potential viral entry as well as cellular toxicological properties. In Chapter 3, a novel series of highly potent and selective CXCR4 antagonists based on a chiral tetrahydroisoquinoline ((R)-THIQ)) scaffold are presented. This novel series made use of a GPCR chemotype with a chiral linkage that may exploit unique and efficient contacts with amino acid residues in the receptor. The data used to elucidate the structure activity relationships (SAR) of this series was generated by a combination of two assays: 1) blockade of HIV-1IIIB attachment via the CXCR4 receptor in MAGI cells, and 2) inhibition of CXCL12 induced calcium (Ca2+) flux/release in Chem-1 cells. The compounds revealed a range of potencies and divergent SAR. The motif also provided compounds with unique biological selectivity and provided exciting insights for the design of X4-tropic HIV-1 selective modulators that do not interfere with CXCL12 based receptor signaling.

The CXCR4 receptor has a specific role in a wide range of human disease pathologies, but the interaction between CXCR4 and its natural ligand CXCL12 also synchronizes many essential physiological roles. Therefore, selective inhibition of X4-tropic HIV-1 entry without compromising the physiologically important signaling between CXCR4 and CXCL12 is crucial and therapeutically relevant. In Chapter 4, we describe the synthesis and biological activity of a new class of CXCR4 modulators. Within this series of compounds, certain analogues were identified with 2500-fold selectivity for blocking X4-tropic HIV-1 entry over inhibition of CXCL12 induced calcium flux. These compounds represent a novel class of CXCR4 modulators.

Table of Contents

Table of Contents

List of Illustrations

List of Graphs

Chapter 1: Introduction and Background

1.1 CXCR4 and the Natural Ligand CXCL12 1
1.1.2 CXCX4 and CXCL12 Structures 3
1.1.3 Two-Site Ligand Binding 5
1.1.4 Signaling 6

1.2 Therapeutic Uses of CXCR4 Antagonists
1.2.1 HIV Infection 8
1.2.2 Stem Cell Mobilization 9

Chapter 2: Design of Novel AMD3100 Analogs

2.1 Statement of Purpose 15
2.2 Introduction and Background 16
2.3 Design Rational 19
2.4 Discussion & Biological Evaluation 21
2.5 Conclusions 29
2.6 Chemistry Experimental 30
2.7 Biological Experimental 45

Chapter 3: Design of 1,2,3,4-tetrahydroisoquinoline-based CXCR4 Antagonists

3.1 Statement of Purpose 50
3.2 Introduction and Background 51
3.3 Design Rational 58
3.3.1 Tetrahydroisoquinoline Modifications 61
3.3.2 Butyl amine side chain Modifications 72
3.4 Discussion & Biological Evaluation 68
3.5 Conclusions 78
3.6 Chemistry Experimental 79
3.7 Biological Experimental 137

Chapter 4: Design of Novel First-In-Class CXCR4 Allosteric Modulators

4.1 Statement of Purpose 147
4.2 Introduction and Background 149
4.3 Design Rational 151
4.4 Discussion & Biological Evaluation 152
4.5 Conclusions 157
4.6 Chemistry Experimental 158
4.7 Biological Experimental 187

List of Illustrations

List of Figures

Figure 1.1: Cartoon representation of CXCR4-IT1t structure 3
Figure 1.2: Cartoon representation of CXCL12 (SDF-1) 4
Figure 1.3: Proposed 2-step mechanism of the CXCR4/CXCL12 binding 5
Figure 1.4: CXCR4 signaling pathways 6
Figure 1.5: Mechanism of HIV-1 entry 8
Figure 1.6: Mechanism of stem cell mobilization 9
Figure 2.1: Structures of CXCR4 antagonists 15
Figure 2.2: Proposed binding mode of AMD3100 with CXCR4 17
Figure 2.3: CXCR4 antagonist template used to generate AMD3100 analogs 18
Figure 2.4: WZ-41 structure 18
Figure 2.5: Structures of select bioactive products that incorporate the bis-THF moiety 19
Figure 2.6: Structures of Brecanavir and Darunavir 20
Figure 2.7: Interaction in x-ray crystal structure of Darunavir bound to HIV protease 20
Figure 3.1: Selected orally bioavailable small-molecule CXCR4 antagonists. 50
Figure 3.2: Initial hit-to-lead efforts and general conclusions 52
Figure 3.3: General conclusions on initial hit-to-lead efforts. 53
Figure 3.4: Conclusions on hit-to-lead efforts 54
Figure 3.5: Overview of proposed N-THIQ and butyl amine analogs 57
Figure 3.6: Advanced intermediate scaffold 58
Figure 3.7: Retrosynthesis of N-TIC analogs 59
Figure 3.8: Retrosynthesis of butyl amine analogs 92-95 64
Figure 4.1: Tetrahydroisoquinoline-based selective HIV compounds
Figure 4.2: Allosteric and orthosteric ligands of G protein-coupled receptors; range of possible activities 65

List of Tables

Table 2.1: Biological data for compounds 25, 29, 34, 36 & 41 21
Table 3.1: Tetrahydroisoquinoline analogs 45-64 70
Table 3.2: Butyl amine analogs 74-84 71
Table 3.3: Butyl amine analogs 92-95 72
Table 3.4: Butyl amine analogs 102, 104, 108, & 109 73
Table 4.1: Tetrahydroisoquinoline analogs 125-139 155

List of Schemes

Scheme 2.1: Strategy for asymmetric synthesis of bis-THF alcohol 21
Scheme 2.2: Synthesis of fragment A1 22
Scheme 2.3: Retrosynthesis of bis-THF analogs 23
Scheme 2.4: Synthesis of fragment B1 24
Scheme 2.5: Synthesis of fragments A2 and A3 25
Scheme 2.6: Synthesis of analog 29 25
Scheme 2.7: Synthesis of fragment B2 26
Scheme 2.9: Synthesis of analog 41 27
Scheme 3.1: Synthesis of (S)-5,6,7,8-tetrahydroquinolin-8-amine 59
Scheme 3.2: Synthesis 4-(1,3,-dioxoisoindolin-2-yl)butanol 60
Scheme 3.3: Synthesis of (R)-tert-butyl 3-formyl-3,4-dihydroisoquinoline-2(1H)
-carboxylate 60
Scheme 3.4: Synthesis of N-THIQ analogs 45-59 61
Scheme 3.5: Synthesis of N-THIQ morpholine analog 63 62
Scheme 3.6: Synthesis of butyl amine analogs 74-82 63
Scheme 3.7: Synthesis of butyl amine analog 84 64
Scheme 3.8: Synthesis of butyl amine analogs 102 & 104 65
Scheme 3.9: Synthesis of butyl amine analogs 108 & 109 66
Scheme 4.1: Synthesis of N-THIQ analogs 125-139 152
Table 4.1: Tetrahydroisoquinoline analogs 125-139 155

List of Graphs

4.1: Inhibition of HIV-IIIB replication in PBMCs by 137 181
4.2: Cytochrome P450 Assay on compound 137 182
4.3: Displacement of 125I-SDF-1 binding by compound 137 185

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