Supramolecular Synthons in Crystal Engineering of Pharmaceutical Properties

Ashwini Nangia (born 1960) is a senior professor of chemistry at the University of Hyderabad, India. He completed his MSc from Indian Institute of Technology Kanpur (1983) and PhD from Yale University (1988). He joined the University of Hyderabad in 1989 and was promoted to professor in 2002 and to senior professor in 2019. His research interests in crystal engineering include polymorphs, cocrystals, salts, eutectics, and amorphous forms of drugs and pharmaceuticals. He has authored more than 350 research publications, with over 18,000 citations and an h-index of 70. He is a fellow of the three premier National Science Academies of India and Royal Society of Chemistry, London. He is a recipient of the prestigious JC Bose National Fellowship. He was director of Council of Scientific and Industrial Research–National Chemical Laboratory, Pune from March 2016 to November 2020, during which time he diversified his interests to flow chemistry and process intensification in crystallization.

Chapter 1 Introduction to Supramolecular Chemistry and Crystal Engineering

1.1 Introduction

1.2 Organic synthesis

1.3 Supramolecular chemistry

1.4 Crystal engineering

1.5 Hydrogen bonding

1.6 Space groups

1.7 Summary conclusions

1.8 References

1.9 Questions and thoughts

1.10 Additional reading

Chapter 2 Crystal Engineering, Supramolecular Synthons, and Cocrystal Design

2.1 Introduction

2.2 Supramolecular synthons

2.3 Crystal engineering of pharmaceutical cocrystals

2.3.1 Cocrystals

2.3.2 Pharmaceutical cocrystals

2.4 Cocrystal design approaches

2.4.1 Hydrogen bond synthons

2.4.2 ΔpKa rule

2.4.3 Computational methods

2.4.4 Molecular electrostatic potential surface energy

2.4.5 Hansen solubility parameter

2.5 Summary conclusions

2.6 References

2.7 Questions and thoughts

Chapter 3 Pharmaceutical Solid-State Forms

3.1 Introduction

3.2 Pharmaceutical multi-component crystals

3.2.1 Drug salts and pharmaceutical cocrystals

3.2.2 Pharmaceutical cocrystals via crystal engineering

3.2.3 Coamorphous solids

3.2.4 Solid solutions and eutectics

3.2.5 Ionic liquids

3.2.6 Ionic cocrystals

3.2.7 Nanocrystalline drugs

3.2.8 Supramolecular gels of drugs

3.2.9 Salt−cocrystal continuum or hybrid quasi-state of proton

3.2.10 Cocrystal polymorphs

3.2.11 Ternary and higher organic cocrystals

3.3 Summary conclusions

3.4 References

3.5 Questions and thoughts

Chapter 4 Design and Methodology of Pharmaceutical Cocrystals

4.1 Introduction

4.2 Complementarity between API and coformer

4.3 Preparation methods of cocrystals

4.3.1 Spray drying

4.3.2 Freeze drying

4.3.3 Hot melt extrusion

4.3.4 Rotary evaporator method

4.3.5 Vapor-assisted tumbling

4.4 Drug−drug cocrystals

4.5 Drug−nutraceutical cocrystals

4.6 Ternary and higher order cocrystals

4.7 Cocrystals of different stoichiometry

4.8 Zwitterionic cocrystals

4.9 Halogen-bonded pharmaceutical cocrystals

4.10 Characterization methods of cocrystals

4.11 Summary conclusions

4.12 References

4.13 Questions and thoughts

Chapter 5 Applications of Pharmaceutical Cocrystals

5.1 Introduction

5.2 Bioavailability improvement

5.3 Hydration stability

5.4 Chemical degradation stability

5.5 Tableting

5.6 Mechanical properties

5.7 Phase diagram and solubility measurements

5.8 Permeability and plasma concentration

5.9 Spring and Parachute model

5.10 Summary conclusions

5.11 References

5.12 Questions and thoughts

Chapter 6 Continuous Manufacturing of Cocrystals and Salts

6.1 Introduction

6.2 Batch and flow chemistry

6.3 Flow chemistry and pharmaceutical cocrystals manufacturing

6.4 Case studies of pharmaceutical cocrystals and salts

6.5 Continuous process technologies

6.6 Flow guide for the synthetic chemist

6.7 Summary conclusions

6.8 References

6.9 Questions and thoughts

Chapter 7 Commercial Outlook of Pharmaceutical Cocrystals

7.1 Introduction

7.2 Present status

7.3 Patenting and regulatory aspects

7.4 Entresto® drug-drug cocrystal salt

7.5 Seglentis® US-FDA approval

7.6 Summary conclusions

7.7 References

7.8 Questions and thoughts

Chapter 8 Controlling Polymorphism

8.1 Introduction

8.2 Definition and importance

8.3 Polymorphism and cocrystallization

8.4 Tailored additives to control crystal size and morphology

8.5 Summary conclusions

8.6 References

8.7 Questions and thoughts

Chapter 9 Supramolecular Heterosynthon in High Bioavailability Drugs

9.1 Introduction

9.2 Common heterosynthons in drugs

9.3 Heterosynthon model for high bioavailability drugs

9.4 Models for permeability enhancement

9.5 Cocrystal drugs beyond the Rule of 5

9.6 Improving cell penetration by atom replacement

9.7 Summary conclusions

9.9 Questions and thoughts

Chapter 10 Other Applications of Cocrystals

10.1 Introduction

10.2 Property engineering

10.3 Mechanochemistry

10.4 Energetic cocrystals

10.5 Summary conclusions

10.6 References

10.7 Questions and thoughts

Chapter 11 AI ML ChatGPT in Chemistry

11.1 Introduction

11.2 Retrosynthetic reaction prediction

11.3 Medicinal molecules

11.4 MOFs and inorganic materials

11.5 Cocrystals

11.6 Summary conclusions

11.7 References

11.8 Questions and thoughts

Chapter 12 3D Electron Diffraction

12.1 Introduction

12.2 Advantages of ED

12.3 Resurgence of ED

12.4 New pharmaceutical challenges solved by ED

12.5 Summary conclusions

12.6 References

12.7 Questions and thoughts

Chapter 13 Challenges, Conclusions, and Future Directions

13.1 Introduction

13.2 Carboxamide−pyridine-N-oxide heterosynthon

13.3 Browsing the literature

13.4 Challenges in pharmaceutical cocrystal technology

13.5 Conclusions

13.6 References

13.7 Suggested reading

Index