Synthesis of 5‐ethyl‐2‐{5‐[4‐(2‐hydroxyethyl)piperazin‐1‐ylsulfonyl]‐2‐n‐propoxyphenyl}‐7‐n‐propyl‐3,5‐dihydro‐4H‐pyrrolo[3,2‐d]‐[2‐¹⁴C]pyrimidin‐4‐one·2 HCl (¹⁴C‐SK3530·2 HCl)

A new 14 C‐labelled PDE5 inhibitor, 5‐ethyl‐2‐{5‐[4‐(2‐hydroxyethyl)piperazin‐1‐ylsulfonyl]‐2‐ n ‐propoxyphenyl}‐7‐ n ‐propyl‐3,5‐dihydro‐4 H ‐pyrrolo[3,2‐ d ]‐[2‐ 14 C]pyrimidin‐4‐one·2 HCl ( 14 C‐SK3530·2 HCl) ( 1· 2 HCl) was synthesized through a straightforward six‐step sequence from the readily available [ 14 C‐carbonyl]methyl salicylate ( 2 ). The overall radiochemical yield of the 1· 2 HCl from 2 was 10.5%, and its radiochemical purity was 98.8%.