A process for the preparation of a compound of formula (I): ##STR1## which comprises cyclization of a compound of formula (II): ##STR2##

A process for the preparation of a compound of formula (I): ##STR1## which comprises cyclization of a compound of formula (II): ##STR2##

A polymorph of 1-{6-ethoxy-5-[3-ethyl-6,7-dihydro-2-(2-methoxyethyl)-7-oxo-2H-pyrazolo[4, 3-d]pyrimidin-5-yl]-3-pyridylsulfonyl}-4-ethylpiperazine.

A process for the preparation of Compounds of the formula (1): ##STR00001## wherein R.sup.1, R.sup.2, R.sup.4 and R.sup.13 are as defined or a pharmaceutically or veterinarily acceptable salt or polymorph thereof, or a pharmaceutically or veterinarily acceptable solvate or pro-drug thereof: are potent and selective inhibitors of type 5 cyclic guanosine 3',5'-monophosphate phosphodiestbrase (cGMP PDE5) and have utility in the treatment of, inter alia, male erectile dysfunction (MED) and female se...

Compounds of the formula (I): ##STR1## wherein R.sup.1, R.sup.2, R.sup.4 and R.sup.13 are as defined or a pharmaceutically or veterinarily acceptable salt or polymorph thereof, or a pharmaceutically or veterinarily acceptable solvate or pro-drug thereof: are potent and selective inhibitors of type 5 cyclic guanosine 3',5'-monophosphate phosphodiesterase (cGMP PDE5) and have utility in the treatment of, inter alia, male erectile dysfunction (MED) and female sexual dysfunction (FSD).

A process is provide for the preparation of compounds of formula (I) herein ##STR1## comprising reacting a compound of formula (III), (IV) or (V) ##STR2## wherein the variables are as defined in the specification. The reaction is conducted in the presence of .sup.- OR.sup.3 and a hydroxide trapping agent or in the case of compounds of formula (IV) reacting in the presence of an auxiliary base and a hydroxide trapping agent.