Investigation of Synthetic Routes to a Key Benzopyran Intermediate of a 5HT(4) Agonist

The supply route to GlaxoSmithKline's 5HT(4) receptor agonist 1 centred on the construction of key benzopyran fragment 2. Our attempts to define the final manufacturing route for this component are described through it series of disconnections. The systematic approach undertaken towards the construction of the benzopyran skeleton focused on cyclisation strategies front appropriate precursors and evaluation of the performance of the key steps.