A green chemistry perspective on catalytic amide bond formation

An analysis of chemical reactions used in current medicinal chemistry (2014), three decades ago (1984), and in natural product total synthesis has been conducted. The analysis revealed that of the current most frequently used synthetic reactions, none were discovered within the past 20 years and only two in the 1980s and 1990s (Suzuki-Miyaura and Buchwald-Hartwig). This suggests an inherent high bar of impact for new synthetic reactions in drug discovery. The most frequently used reactions were amide bond formation, Suzuki-Miyaura coupling, and SNAr reactions, most likely due to commercial availability of reagents, high chemoselectivity, and a pressure on delivery. We show that these practices result in overpopulation of certain types of molecular shapes to the exclusion of others using simple PMI plots. We hope that these results will help catalyze improvements in integration of new synthetic methodologies as well as new library design.

A methodology, based on a combination of SH&E criteria, enables a simplified greenness evaluation of any solvent, in the context of fine or pharmaceutical chemistry.

The purpose of this perspective is to indicate the range of chemistries used in the manufacture of drug candidate molecules and to highlight certain gaps in current technologies. To do this a survey was carried out of chemical syntheses within the Process Chemistry R&D departments of GlaxoSmithKline, AstraZeneca and Pfizer.