La. Van Vliet et al., Thiazoloindans and thiazolobenzopyrans: A novel class of orally active central dopamine (partial) agonists, J MED CHEM, 43(19), 2000, pp. 3549-3557
The 2-aminothiazole moiety has proven its value in medicinal chemistry as a
stable and lipophilic bioisosteric replacement of a phenol group. This app
roach has provided dopamine (DA) agonists with good oral availability. To f
urther explore its use in the development of DA agonists, we have combined
the 2-aminothiazole moiety with 2-aminoindans and 3-aminobenzopyrans, which
are known templates for DA agonists. In this study we have synthesized 6-a
mino-3-(N,N-di-n-propylamino)-3,4-dihydro-2H-thiazole[5,4-f]-[1]benzopyran
(12) and 6-amino-2-(N,N-di-n-propylamino)thiazolo[4,5-f]indan (20) and seve
ral analogues (13, 17, and 21). The affinity of the thiazolobenzopyrans and
thiazoloindans for DA receptors was evaluated, which revealed compound 20
to have high affinity for DA DQ receptors. In addition, the compounds were
screened for their potential to inhibit lipid peroxidation, to determine th
eir radical scavenging properties. Compounds 12, 20, and 21 were subjected
to further pharmacological evaluation in a functional assay to determine in
trinsic activity. Compound 20 was also studied with microdialysis (to deter
mine effects on DA turnover in striatum) and in unilaterally 6-OH-DA lesion
ed rats (to determine their potential as DA agonists). These studies select
ed compound 20 (GMC 1111) as particularly interesting. Compound 20 caused a
rotation activation in unilaterally B-OH-DA lesioned rats and an increase
in DA turnover in rat striatum. This dual agonist/antagonist action is best
accounted for by its partial agonism at striatal DA D-2 receptors. Interes
tingly, 20 displayed long-lasting activity and excellent oral availability
in B-OH-DA lesioned rats, making this compound potentially useful for the t
reatment of Parkinson's disease.