Isolation and identification of a new sildenafil analogue adulterated in energy drink: propoxyphenyl sildenafil

A new sildenafil analogue was found to be added illegally to a energy drink marketed for the enhancement of sexual function. The structure was determined as 1-[4-propoxy-3-(6,7-dihydro-1-methyl-7-oxo-3-propyl-1H-pyrazolo[4,3-d]pyrimidin-5-yl)phenylsulfonyl]-4-methylpiperazine. Owing to the inclusion of one more methyl group to sildenafil (on C-21), the detected compound was called "propoxyphenyl sildenafil". The sample was purified with column chromatography. The UV, IR, LC/MS (ESI) and completely assigned NMR data of propoxyphenyl sildenafil is reported. Having compared the structure with sildenafil, the results showed that the 2-ethoxy group (at the position on C-19) has been replaced by propoxy group.