A divergent approach to the pyrroloquinoline
scaffold as present
in the class of Aspidosperma alkaloids was developed.
As a case study, abundant and renewable nicotinic acid was transformed
via pericyclic framework reconstruction into aspidodispermine, a unique
member of pyrroloquinoline alkaloids. The sequence comprises a [2
+ 2]-photocycloaddition, a Ramberg–Bäcklund contraction,
and a strain-promoted formal electrocyclic rearrangement of a bicyclo[2.2.0]hexene
and is potentially extendable to pyrroloindole scaffolds as present
in the ibophyllidine alkaloids.