Acta Cryst. (2005). E61, o489-o491  [ doi:10.1107/S1600536805002564 ]

Sildenafil citrate monohydrate

H. S. Yathirajan, B. Nagaraj, P. Nagaraja and M. Bolte

Abstract: Sildenafil citrate is well known as Viagra for the treatment of erectile dysfuncion. In the title compound (systematic name: 1-{[3-(6,7-Dihydro-1-methyl-7-oxo-3-propyl-1H-pyrazolo[4,3-d]pyrimidin-5-yl)-4-ethoxyphenyl]sulfonyl}-4-methylpiperazinium citrate monohydrate), C₂₂H₃₁N₆O₄S⁺·C₆H₇O₇^-·H₂O, the pyrazolopyrimidone ring system and the benzene ring are almost coplanar, enabling an intramolecular hydrogen bond between the pyrazolopyrimidone NH group and the O atom of the ethoxy group. One of the N atoms of the piperazine ring is protonated and the citrate molecule exists as an anion. The crystal packing is stabilized by several hydrogen bonds.

Online 29 January 2005

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