Importance and review of drug metabolite synthesis

Phase I and Phase II metabolic reactions are involved in the pharmacokinetic properties of drugs after administration. These reactions mainly aim to make drugs more polar and eliminate them safely. However, some of these metabolites have the potential to exhibit a toxicological effect. Industry and/or academia have to consider these metabolites in terms of their pharmacodynamic and pharmacokinetic properties. These metabolites are not only residual intermediates from the synthetic process of the main drug but also unique structures produced by metabolic enzymes in the human organism. Thus, metabolite synthesis by synthetic or semi-synthetic methods is a key feature in the pharmaceutical industry. In this review, synthetic methods of the metabolites from all known metabolic pathways are reviewed from the literature. It was observed that both synthetic and semi-synthetic methods require more attention as they are as important and complex as drug synthesis. Moreover, it showed that there was much more research available for Phase I than Phase II in the literature.