A machine-assisted approach for the preparation of follow-on pharmaceutical compound libraries

Follow-on drugs represent the majority of new drug introductions and show improved properties to the pioneer drug. In order to fast-follow, R&D needs to be able to quickly generate a library of analogues that can then be screened for desired properties. Here we have designed a hybrid machine-assisted approach which makes use of both multi-step continuous flow processing and robotic microwave reactors to generate a library of indoles over two technology steps (four reaction steps; diazotization, reduction, unmasking of the hydrazine and Fischer indole reaction). This ‘machine’ is then used to prepare a small library of hitherto unreported analogues of the 5-HT agonist Zolmitriptan in good yields, thus demonstrating that the integration and use of machines is a powerful tool to expedite drug discovery.