Design, synthesis and biological activity of β-carboline-based type-5 phosphodiesterase inhibitors

The SAR of a series of β-carboline derived type 5 phosphodiesterase inhibitors has been explored and we have discovered compounds with excellent levels of PDE5 potency and selectivity over PDE6. However, the series exhibits low levels of selectivity over PDE11, a phosphodiesterase with unknown function.