Estulic,Sandoz,Switz.,1980
Centrally acting α-adrenoceptor agonist. Antihypertensive.
Guanfacine centrally acting α-adrenoceptor agonist. Guanfacine is an antihypertensive.
ChEBI: Guanfacine is a member of acetamides.
2,6-Dichlorophenyl-acetyl-guanidine: A solution of 3.245 g (0.055 mol) of
guanidine in isopropanol is added to a solution of 11.7 g (0.05 mol) of 2,6-
dichlorophenyl-acetic acid ethyl ester (BP 142°C to 143°C/12 mm of Hg) in
20cc of isopropanol. The reaction mixture is allowed to stand overnight and is
subsequently concentrated by evaporation. After recrystallizing the residue
from methanol/ether 2,6-dichlorophenyl-acetyl-guanidine is obtained in the
form of white grains having a MP of 225°C to 227°C.
2,6-Dichlorophenyl-acetyl-guanidine hydrochloride: A solution of 5.6 g (0.025
mol) of 2,-dichlorophenylacetic acid chloride (BP 137°C to 138°C/12 mm of
Hg) in 10 cc of toluene is added dropwise to a mixture of 4.5 g (0.076 mol) of
guanidine and 60 cc of toluene. The reaction mixture is allowed to stand at
room temperature for 20 minutes, is then heated on a steam bath for 2 hours
and is subsequently cooled. The resulting precipitate is filtered off and washed
twice with 25 cc amounts of water in order to separate the guanidine
hydrochloride. The residue (2,6-dichlorophenyl-acetyl-guanidine) is washed
with chloroform for further purification and is then dissolved in 50 cc of
isopropanol. The pH-value of the solution is adjusted to 6 with ethanolic
hydrochloric acid and the solution is cooled. The resulting white needles are
again washed with chloroform. The resulting 2.6-dichlorophenyl-acetylguanidine hydrochloride has a MP of 213°C to 216°C.
Guanfacine is more selective for 2-receptors than isclonidine. Their mechanism of action is the same as that ofclonidine. Differences between clonidine and its twoanalogs are seen in their elimination half-life values and intheir metabolism and urinary excretion patterns. The eliminationhalf-life of clonidine ranges from 20 to 25 hours,whereas that for guanfacine is about 17 hours. Guanabenzhas the shortest DOA of these three agents, with a half-lifeof about 6 hours. Clonidine and guanfacine are excretedunchanged in the urine to the extent of 60% and 50%,respectively. Very little of guanabenz is excreted unchangedin the urine.
Guanfacin, N-amidino-2-(2,6-dichlorophenyl)acetamide (22.3.2), is also synthesized
in a very easy synthesis of reacting the acid chloride or ester of 2,6-
dichlorophenylacetic acid with guanidine.
