A comprehensive guide to privileged structures and their application in the discovery of new drugs
The use of privileged structures is a viable strategy in the discovery of new medicines at the lead optimization stages of the drug discovery process. Privileged Structures in Drug Discovery offers a comprehensive text that reviews privileged structures from the point of view of medicinal chemistry and contains the synthetic routes to these structures. In this text, the author - a noted expert in the field - includes an historical perspective on the topic, presents a practical compendium to privileged structures, and offers an informed perspective on the future direction for the field.
The book describes the up-to-date and state-of-the-art methods of organic synthesis that describe the use of privileged structures that are of most interest. Chapters included information on benzodiazepines, 1,4-dihydropyridines, biaryls, 4-(hetero)arylpiperidines, spiropiperidines, 2-aminopyrimidines, 2-aminothiazoles, 2-(hetero)arylindoles, tetrahydroisoquinolines, 2,2-dimethylbenzopyrans, hydroxamates, and bicyclic pyridines containing ring-junction nitrogen as privileged scaffolds in medicinal chemistry. Numerous, illustrative case studies document the current use of the privileged structures in the discovery of drugs. This important volume:
- Describes the drug compounds that have successfully made it to the marketplace and the chemistry associated with them
- Offers the experience from an author who has worked in many therapeutic areas of medicinal chemistry
- Details many of the recent developments in organic chemistry that prepare target molecules
- Includes a wealth of medicinal chemistry case studies that clearly illustrate the use of privileged structures
Designed for use by industrial medicinal chemists and process chemists, academic organic and medicinal chemists, as well as chemistry students and faculty, Privileged Structures in Drug Discovery offers a current guide to organic synthesis methods to access the privileged structures of interest, and contains medicinal chemistry case studies that document their application.
Table of Contents
1 Introduction 1
1.1 The Original Definition of Privileged Structures 1
1.2 The Role of Privileged Structures in the Drug Discovery Process 1
1.3 The Loose Definitions of “Privileged Structures” 2
1.4 Synthesis and Biological Activities of Carbocyclic and Heterocyclic Privileged Structures 2
1.4.1 Synthesis and Biological Activities of ThreeÂ] and FourÂ]Membered Ring Privileged Structures 2
1.4.2 Synthesis and Biological Activities of Five-Membered Ring Privileged Structures 2
1.4.3 Synthesis and Biological Activities of Six-Membered Ring Privileged Structures 4
1.4.4 Synthesis and Biological Activities of Bicyclic 5/5 and 6/5 Ring Privileged Structures 4
1.4.5 Synthesis and Biological Activities of Bicyclic 6/6 and 6/7 Ring Privileged Structures 4
1.4.6 Synthesis and Biological Activities of Tricyclic and Tetracyclic Ring Privileged Structures 4
1.5 Combinatorial Libraries of “Privileged Structures” 4
1.6 Scope of this Monograph 9
References 10
2 Benzodiazepines 15
2.1 Introduction 15
2.2 Marketed BDZ Drugs 15
2.2.1 1,4-Benzodiazepine Marketed Drugs 15
2.2.2 1,5-Benzodiazepine Marketed Drugs 16
2.2.3 Linearly Fused BDZ Marketed Drugs 16
2.2.4 Angularly Fused-1,4-Benzodiazepine Marketed Drugs 17
2.3 Medicinal Chemistry Case Studies 17
2.3.1 Cardiovascular Applications 17
2.3.2 Central Nervous System Applications 19
2.3.3 Gastrointestinal Applications 23
2.3.4 Infectious Diseases Applications 24
2.3.5 Inflammation Applications 25
2.3.6 Metabolic Diseases Applications 27
2.3.7 Oncology Applications 28
2.4 Synthesis of BDZs 30
2.4.1 Condensation of o-Phenylenediamines to 1,5-Benzodiazepines 31
2.4.1.1 Condensation of o-Phenylenediamines with Ketones 31
2.4.1.2 Condensation of o-Phenylenediamines with α,β-Unsaturated Ketones 33
2.4.1.3 Condensation of o-Phenylenediamines with Alkynes 34
2.4.2 Reductive Condensation of α-Substituted Nitrobenzenes with Ketones and α,β-Unsaturated Ketones 35
2.4.3 Intramolecular Cyclizations to 1,4-Benzodiazepines 35
2.4.3.1 Intramolecular Cyclizations - Path A 36
2.4.3.2 Intramolecular Cyclizations - Path B 37
2.4.3.3 Intramolecular Cyclizations - Path C 39
2.4.3.4 Intramolecular Cyclizations - Path D 40
2.4.3.5 Intramolecular Cyclizations - Path E 42
2.4.3.6 Intramolecular Cyclizations - Path F 42
2.4.3.7 Intramolecular Cyclizations - Path G 42
2.4.3.8 Intramolecular Cyclizations - Path H 42
2.4.4 Ugi Multicomponent Synthesis 42
2.4.5 Elaboration of 1,4-Benzodiazepines 44
2.4.6 Pyrrolo[2,1-c]benzodiazepines 45
2.4.7 Fused BDZ Ring Systems 45
2.4.8 Solid-Phase Synthesis of BDZs 47
References 47
3 1,4-Dihydropyridines 59
3.1 Introduction 59
3.2 Marketed 1,4-Dihyropyridine Drugs 59
3.3 Medicinal Chemistry Case Studies 59
3.3.1 Cardiovascular Applications 59
3.3.2 Central Nervous System Applications 61
3.3.3 Infectious Diseases Applications 62
3.3.4 Inflammation Applications 63
3.3.5 Men’s and Women’s Health Issues Applications 64
3.3.6 Metabolic Diseases Applications 65
3.3.7 Oncology Applications 65
3.4 Synthesis of 1,4-Dihydropyridines 66
3.4.1 Classical Hantzsch Synthesis 66
3.4.2 Modified Hantzsch Conditions 66
3.4.3 1,4-Disubstituted-1,4-Dihydropyridines 69
3.4.4 Organometallic Additions to Pyridinium Salts 69
3.4.5 From Imines and Enamino Compounds 71
3.4.6 Multicomponent Synthesis 72
3.4.6.1 Three-Component Synthesis of 1,4-Dihydropyridines 72
3.4.6.2 Four-Component Synthesis of 1,4-Dihydropyridines 74
3.4.7 Organocatalytic Synthesis of 1,4-Dihydropyridines 74
3.4.8 Miscellaneous Preparations 75
3.4.9 Elaboration of 1,4-Dihydropyridines 76
References 77
4 Biaryls 83
4.1 Introduction 83
4.2 Marketed Biaryl Drugs 83
4.3 Medicinal Chemistry Case Studies 87
4.3.1 Cardiovascular Applications 87
4.3.2 Central Nervous System Applications 89
4.3.3 Infectious Diseases Applications 95
4.3.4 Inflammation Applications 98
4.3.5 Men’s and Women’s Health Issues Applications 102
4.3.6 Metabolic Diseases Applications 103
4.3.7 Oncology Applications 109
4.4 Synthesis of Biaryls 114
4.4.1 Transition Metal-Catalyzed Cross‑Coupling Synthesis 114
4.4.1.1 Suzuki–Miyaura Cross-Coupling Reactions with Boronic Acids 114
4.4.1.2 Suzuki–Miyaura Cross-Coupling Reactions with Boronate Esters 114
4.4.1.3 Metal-Catalyzed Homocoupling Reactions 121
4.4.1.4 Uhlmann Coupling Reactions 122
4.4.1.5 Kumada–Tamao–Corriu Cross-Coupling Reactions 123
4.4.1.6 Negishi Cross-Coupling Reactions 124
4.4.1.7 Hiyama Cross-Coupling Reactions 124
4.4.1.8 Stille Cross-Coupling Reactions 125
4.4.1.9 Miscellaneous Cross-Coupling Reactions 126
4.4.1.10 Metal-Catalyzed Functional Group Removal Cross-Coupling Reaction 127
4.4.2 C„ŸH Functionalization Reactions 127
4.4.2.1 Oxidative Coupling Reactions 127
4.4.2.2 Direct C„ŸH Arylations 127
4.4.2.3 C„ŸH Functionalization with Directing Groups 127
4.4.3 Cycloaddition Reactions 132
4.4.3.1 [3+3] Cycloaddition Reactions 132
4.4.3.2 [4+2] Cycloaddition Reactions 132
4.4.3.3 [2+2+2] Cycloaddition Reactions 133
4.4.3.4 Tandem Cycloaddition Reactions 133
4.4.4 Biaryl Phenol Syntheses 133
4.4.5 Miscellaneous Syntheses 134
References 135
5 4-(Hetero)Arylpiperidines 155
5.1 Introduction 155
5.2 Marketed 4-(Hetero)Arylpiperidine Drugs 155
5.3 Medicinal Chemistry Case Studies 159
5.3.1 Cardiovascular Applications 159
5.3.2 Central Nervous System Applications 159
5.3.3 Infectious Diseases Applications 168
5.3.4 Inflammation Applications 169
5.3.5 Men’s and Women’s Health Applications 174
5.3.6 Metabolic Diseases Applications 175
5.3.7 Oncology Applications 177
5.4 Synthesis of 4-(Hetero)Arylpiperidines 179
5.4.1 Preparation from 4-Piperidinones 179
5.4.2 Preparation from 4-Prefunctionalized-3-alkenylpiperidines 180
5.4.3 Preparation from Negishi Cross-Coupling of 3-Zincated Piperidines 180
5.4.4 Preparation from 4-Funtionalized Piperidines 181
5.4.5 Conjugated Addition to Unsaturated Piperidines 181
5.4.6 Miscellaneous Syntheses 183
References 185
6 Spiropiperidines 194
6.1 Introduction 194
6.2 Marketed Spiropiperidine Drugs 194
6.3 Medicinal Chemistry Case Studies 195
6.3.1 Cardiovascular Applications 195
6.3.2 Central Nervous System Applications 197
6.3.3 Infectious Diseases Applications 203
6.3.4 Inflammation Applications 205
6.3.5 Men’s and Women’s Health Applications 210
6.3.6 Metabolic Diseases Applications 211
6.3.7 Oncology Applications 216
6.4 Synthesis of Spiropiperidines 218
6.4.1 Quinolinylspiropiperidines 218
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6.4.2 Azaspiro[5.5]alkane Systems 218
6.4.3 Diazaspiro[5.5]alkane Derivatives 221
6.4.4 1,4-Benzodioxinylspiropiperidines 222
6.4.5 Spirobenzooxazinylspiropiperidines 223
6.4.6 (Iso)Quinolinylspiropiperidines 223
6.4.7 Indenospiropiperidines 225
6.4.8 Indolin(on)ylspiropiperidines 225
6.4.9 Cyclohexadienonylspiropiperidines 226
6.4.10 Cyclopenta[b]pyrrolospiropiperidines 226
6.4.11 Chromanylspiropiperidines 226
6.4.12 (Iso)Benzofuran(on)ylspiropiperidines 227
6.4.13 Indenospiropiperidines 227
References 228
7 2-Aminopyrimidines 237
7.1 Introduction 237
7.2 Marketed 2-Aminopyrimidine Drugs 237
7.3 Medicinal Chemistry Case Studies 239
7.3.1 Cardiovascular Applications 239
7.3.2 Central Nervous System Applications 241
7.3.3 Infectious Diseases Applications 245
7.3.4 Inflammation Applications 248
7.3.5 Metabolic Diseases Applications 254
7.3.6 Miscellaneous Applications 255
7.3.7 Oncology Applications 256
7.4 Synthesis of 2-Aminopyrimidines 267
7.4.1 Aminations with 2-Halo or 2,4-Dihalopyrimidines 267
7.4.2 Cross-Coupling Reactions with 2-Aminopyrimidines 270
7.4.3 Aminations with 2-Sulfonylpyrimidines 270
7.4.4 Cyclizations with Guanidines 272
References 272
8 2-Aminothiazoles 284
8.1 Introduction 284
8.2 Marketed 2-Aminothiazole Drugs 284
8.3 Medicinal Chemistry Case Studies 286
8.3.1 Cardiovascular Diseases Applications 286
8.3.2 Central Nervous System Applications 288
8.3.3 Infectious Diseases Applications 292
8.3.4 Inflammation Applications 296
8.3.5 Metabolic Diseases Applications 299
8.3.6 Oncology Applications 301
8.3.7 Miscellaneous Applications 305
8.4 Synthesis of 2-Aminothiazoles 306
8.4.1 Hantzsch Synthesis from α-Functionalized Ketones and Thioureas 306
8.4.2 Hantzsch Synthesis from Ketones and Thioureas 306
8.4.3 Synthesis from α-Haloketones and Thiocyanates 308
8.4.4 Synthesis from Vinyl Azides and Thiocyanates 308
8.4.5 Synthesis from Amidines and Thiocyanates 309
8.4.6 Synthesis from Alkenyl and Alkynyl Compounds with Thiocyanates or Thioureas 309
8.4.7 Miscellaneous Syntheses 309
8.4.8 Elaboration of 2-Aminothiazoles 311
References 311
9 2-(Hetero)Arylindoles 321
9.1 Introduction 321
9.2 Marketed 2-Arylindole Drugs 321
9.3 Medicinal Chemistry Case Studies 321
9.3.1 Cardiovascular Applications 321
9.3.2 Central Nervous System Applications 322
9.3.3 Infectious Diseases Applications 323
9.3.4 Inflammation Applications 325
9.3.5 Men’s and Women’s Health Applications 326
9.3.6 Metabolic Diseases Applications 328
9.3.7 Miscellaneous Applications 328
9.3.8 Oncology Applications 328
9.4 Synthesis of 2-(Hetero)Arylindoles 332
9.4.1 Functionalization to the Preformed Indole System 332
9.4.1.1 2-Functionalized Metallated Indoles with Aryl Halides (Strategy 1) 332
9.4.1.2 2-Halogenated or 2-Triflated Indoles with Functionalized Arenes (Strategy 1) 332
9.4.1.3 Direct Arylation of Indole with Functionalized Arenes (Strategy 2) 334
9.4.1.4 Direct Oxidative Coupling of Indoles with (Hetero)Arenes (Strategy 3) 334
9.4.2 Fischer Indole Synthesis 334
9.4.3 Bischler–Mohlau Indole Synthesis 334
9.4.4 Metal-Catalyzed Approach with Alkynes 334
9.4.4.1 Intramolecular Cyclizations of o-Alkynylanilines (Strategy A) 336
9.4.4.2 Intramolecular Cyclizations of o-Alkynylanilines with Other Groups (Strategy B) 336
9.4.4.3 Intramolecular Cyclizations of o-Haloanilines with Alkynes (Strategy C) 337
9.4.4.4 Intramolecular Cyclizations of o-Alkynylhaloarenes with Primary Amines (Strategy D) 340
9.4.4.5 Miscellaneous Transition Metal-Catalyzed Reactions 340
9.4.4.6 Reductive Cyclizations of o-Nitroalkynylarenes 342
9.4.5 Intracmolecular Reductive Cyclizations of o-Nitro (or Azido)alkenylarenes 342
9.4.6 Cyclizations of Arylamido and Arylimine Precursors 343
9.4.7 Cyclizations of o-Vinylaminoarenes 344
9.4.8 Cyclizations with N-Arylenamines or N-Arylenaminones 344
9.4.9 Multicomponent Synthesis 345
9.4.10 Radical Cyclization Reactions 346
9.4.11 Miscellaneous Cyclizations with o-Substituted Anilines 346
References 348
10 Tetrahydroisoquinolines 356
10.1 Introduction 356
10.2 Marketed THIQ Drugs 356
10.3 Medicinal Chemistry Case Studies 357
10.3.1 Cardiovascular Applications 357
10.3.2 Central Nervous System Applications 359
10.3.3 Infectious Diseases Applications 365
10.3.4 Inflammation Applications 366
10.3.5 Men’s and Women’s Health Applications 369
10.3.6 Metabolic Diseases Applications 369
10.3.7 Miscellaneous Applications 370
10.3.8 Oncology Applications 372
10.4 Synthesis of THIQs 376
10.4.1 Pictet–Spengler Reactions 376
10.4.1.1 Classical Pictet–Spengler Reactions 376
10.4.1.2 Pictet–Spengler Reactions with Masked Carbonyl Compounds 377
10.4.1.3 Modified Pictet–Spengler Reactions 377
10.4.1.4 Pictet–Spengler-Type Reactions 377
10.4.1.5 Pictet–Spengler Synthesis of Tic 378
10.4.2 Transition Metal-Catalyzed Reactions 379
10.4.2.1 Intramolecular α-Arylation Reactions 379
10.4.2.2 Intramolecular Cyclizations of N-Propargylbenzylamines 379
10.4.2.3 Intramolecular Heck Cyclizations 379
10.4.2.4 Intramolecular Nucleophilic Additions 379
10.4.2.5 One-Pot Multistep Metal-Catalyzed Cyclization Reactions 380
10.4.3 Multicomponent Synthesis of THIQs 382
10.4.4 Synthesis of 3-Aryltetrahydroisoquinolines 382
10.4.5 Synthesis of 4-Aryltetrahydroisoquinolines 383
10.4.6 Miscellaneous Intramolecular Cyclizations 386
10.4.7 Asymmetric Reduction of 1-Substituted-3,4-
Dihydroisoquinolines 387
10.4.7.1 Iridium-Catalyzed Hydrogenations of Dihydroisoquinolines, Isoquinoline Salts, and Isoquinolines 388
10.4.7.2 Ruthenium- and Rhodium-Catalyzed Reductions of Dihydroisoquinolines 389
10.4.7.3 Asymmetric Additions to Dihydroisoquinolines, Dihydroisoquinoline
Salts, and Dihydroisoquinoline N-Oxides 389
10.4.7.4 Asymmetric Intramolecular Cyclizations 391
10.4.7.5 Asymmetric Intramolecular Cyclizations with Chiral Sulfoxides 391
10.4.7.6 Miscellaneous Asymmetric Preparations 392
10.4.8 Arylations of THIQs 393
10.4.9 C„ŸH Functionalization of THIQs 395
10.4.9.1 Direct C-1 (Hetero)Arylations of THIQs 395
10.4.9.2 Oxidative C-1 CDC Reactions 395
10.4.9.3 Oxidative C-1 CDC with β-Ketoesters 396
10.4.9.4 Oxidative C-1 CDC with Ketones 397
10.4.9.5 Oxidative C-1 CDC with Indoles 397
10.4.9.6 Oxidative C-1 CDC with Aliphatic Nitro Compounds 398
10.4.9.7 Oxidative C-1 CDC with Alkynes 399
10.4.9.8 Oxidative C-1 CDC with Alkenes 399
10.4.9.9 Oxidative C-1 Cross-Dehydrogenative Phosphonations 400
10.4.9.10 Miscellaneous Oxidative C-1 CDC Reactions 400
References 401
11 2,2-Dimethylbenzopyrans 414
11.1 Introduction 414
11.2 Marketed 2,2-Dimethylopyran Drugs 414
11.3 Medicinal Chemistry Case Studies 415
11.3.1 Cardiovascular Applications 415
11.3.2 Central Nervous System Applications 416
11.3.3 Infectious Diseases Applications 418
11.3.4 Inflammation Applications 419
11.3.5 Metabolic Diseases Applications 419
11.3.6 Oncology Applications 419
11.3.7 Cannabinoid Receptors 421
11.4 Synthesis of 2,2-Dimethylbenzopyrans 423
11.4.1 Annulations of Phenol Derivatives with Unsaturated Systems 423
11.4.1.1 Annulations of Phenol Derivatives with Simple Alkenes 423
11.4.1.2 Annulations of Phenol Derivatives with α,β-Unsaturated Systems 424
11.4.1.3 Annulations of Phenol Derivatives with Nitroalkenes 424
11.4.1.4 Annulations of Phenol Derivatives with Allylic Alcohols 424
11.4.1.5 Annulations of Phenol Derivatives with Propargyl Alcohols 425
11.4.2 Replacement of the Methyl Group of 2,2-Dimethylbenzopyrans 425
11.4.3 Functionalization of 2,2,-Dimethylbenzopyrans 426
11.4.4 Fused 2,2-Dimethylbenzopyran Ring Systems 428
11.4.5 Solid-Phase Synthesis of 2,2-Dimethylbenzopyrans 428
References 429
12 Hydroxamates 435
12.1 Introduction 435
12.2 Marketed Hydroxame Drugs 435
12.3 Medicinal Chemistry Case Studies 436
12.3.1 Central Nervous System Applications 436
12.3.2 Infectious Diseases Applications 436
12.3.3 Inflammation Applications 439
12.3.4 Men’s and Women’s Health Applications 452
12.3.5 Metabolic Diseases Applications 453
12.3.6 Oncology Applications 453
12.4 Synthesis of Hydroxamates 466
12.4.1 Synthesis of Hydroxamates from Carboxylic Acids 466
12.4.2 Synthesis of Hydroxamates from Carboxylic Acid Derivatives 466
12.4.2.1 Synthesis of Hydroxamates from Esters 466
12.4.2.2 Synthesis of Hydroxamates from Acid Chlorides 468
12.4.2.3 Synthesis of Hydroxamates from Oxazolidinones 468
12.4.3 Miscellaneous Syntheses of Hydroxamates 469
12.4.4 Solid-Phase Synthesis of Hydroxamates 469
References 470
13 Bicyclic Pyridines Containing Ring-Junction Nitrogen 481
13.1 Introduction 481
13.2 Marketed Bicyclic Ring-Junction Pyridine Drugs 481
13.3 Medicinal Chemistry Case Studies 482
13.3.1 Cardiovascular Applications 482
13.3.2 Central Nervous System Applications 483
13.3.3 Gastrointestinal Applications 487
13.3.4 Infectious Diseases Applications 488
13.3.5 Inflammation Applications 491
13.3.6 Metabolic Diseases Applications 493
13.3.7 Miscellaneous Applications 494
13.3.8 Oncology Applications 494
13.4 Synthesis of Pyrazolo[1,5-a]pyridines 498
13.4.1 [3+2] Dipolar Cycloadditions 498
13.4.2 Intramolecular Cyclizations 499
13.4.3 From N-Aminopyridinium Ylides 500
13.4.4 From 2-Substituted Pyridines 500
13.4.5 Thermal and Radical Cyclizations 500
13.5 Synthesis of Imidazo[1,5-a]pyridines 501
13.5.1 From 2-Methylaminopyridines 501
13.5.2 From 2-Methylaminopyridine Amides 502
13.5.3 From 2-Methylaminopyridine Thioamides or Thioureas 503
13.5.4 From Pyridine-2-Carbaldehydes (Picolinaldehydes) 503
13.5.5 From 2-Cyanopyridines 503
13.5.6 From Pyridine-2-Esters 504
13.5.7 From Di-2-Pyridyl Ketones 504
13.5.8 From Pyridotriazoles 504
13.5.9 Miscellaneous Syntheses 504
13.5.10 Chemical Elaborations of Imidazo[1,5-a]pyridines 505
13.6 Synthesis of Imidazo[1,2-a]pyridines 507
13.6.1 Ugi Three-Component Reactions 507
13.6.1.1 Classical Ugi Three-Component Reactions of 2-Aminopyridines, Aldehydes, and (Iso)Nitriles 507
13.6.1.2 Modified Ugi Three-Component Reactions 507
13.6.2 From 2-Aminopyridines and Carbonyl Compounds 509
13.6.2.1 From 2-Aminopyridines and Methyl Ketones 509
13.6.2.2 From 2-Aminopyridines and β-Ketoesters 509
13.6.2.3 From 2-Aminopyridines and Miscellaneous Ketones 510
13.6.2.4 From Pyridines and 2-Aminopyridines with α-Haloketones or α-Haloaldehydes 511
13.6.3 From 2-Aminopyridines and Alkynes 512
13.6.3.1 From 2-Aminopyridines and Alkynes 512
13.6.3.2 From 2-Aminopyridines, Alkynes, and Aldehydes 513
13.6.4 From 2-Aminopyridines and α,β-Unsaturated Systems 513
13.6.5 From 2-Aminopyridines and Nitroolefins 515
13.6.6 Cyclizations from 2-Aminopropargylpyridines 515
13.6.7 Cyclizations from Pyridyl Enamines(ones) 517
13.6.8 From Other Heterocycles 517
13.6.9 Miscellaneous Syntheses 518
13.6.10 Chemical Elaboration of Imidazo[1,2-a]pyridines 520
13.6.10.1 Cross-Coupling Reactions of Pre-functionalized Imidazo[1,2-a]pyridines 520
13.6.10.2 C„ŸH Functionalization of Imidazo[1,2-a]pyridines 521
13.6.11 Fused Imidazo[1,2-a]pyridine Ring Systems 523
References 525
Index
