Novel pyrazolo-tetrahydropyridines as potent orexin receptor antagonists
摘要:
A novel series of dual orexin receptor antagonists was prepared by heteroaromatic five-membered ring system replacement of the dimethoxyphenyl moiety contained in the tetrahydroisoquinoline core skeleton of almorexant. Thus, replacement of the dimethoxyphenyl by a substituted pyrazole and additional optimization of the substitution pattern of the phenethyl motif allowed the identification of potent antagonists with low nanomolar affinity for hOX(1)R and hOX(2)R. The synthesis and structure-activity relationship of these novel antagonists will be discussed in this communication. These investigations furnished several suitable candidates for further evaluation in in vivo studies in rats. (C) 2010 Elsevier Ltd. All rights reserved.
The invention relates to 5,6,7,8-tetrahydro-imidazo[1,5-a]pyrazine derivatives of formula (I), wherein X represents CH
2
or O; R
1
represents a phenyl group, which group is independently mono-, di-, or tri-substituted wherein the substituents are independently selected from the group consisting of (C
1-4
)alkyl, (C
1-4
)alkoxy, halogen, cyano, trifluoromethoxy and trifluoromethyl; R
2
represents (C
1-4
)alkyl, (C
1-4
)alkoxy, (C
2-4
)alkenyl, halogen, cyano, hydroxymethyl, trifluoromethyl, C(O)NR
5
R
6
or cyclopropyl; R
3
represents (C
1-4
)alkyl, (C
1-4
)alkoxy-methyl or halogen; R
4
represents (C
1-4
)alkyl; R
5
represents hydrogen or (C
1-4
)alkyl; and R
6
represents hydrogen or (C
1-4
)alkyl. The invention also relates to pharmaceutically acceptable salts of such compounds; and to the use of such compounds as medicaments; especially as orexin receptor antagonists.
The invention relates to 5,6,7,8-tetrahydro-imidazo[1,5-a]pyrazine derivatives of formula (I), wherein X represents CH2 or O; R1 represents a phenyl group, which group is independently mono-, di-, or tri-substituted wherein the substituents are independently selected from the group consisting of (C1-4)alkyl, (C1-4)alkoxy, halogen, cyano, trifluoromethoxy and trifluoromethyl; R2 represents (C1-4)alkyl, (C1-4)alkoxy, (C2-4)alkenyl, halogen, cyano, hydroxymethyl, trifluoromethyl, C(O)NR5R6 or cyclopropyl; R3 represents (C1-4)alkyl, (C1-4)alkoxy-methyl or halogen; R4 represents (C1-4)alkyl; R5 represents hydrogen or (C1-4)alkyl; and R6 represents hydrogen or (C1-4)alkyl. The invention also relates to pharmaceutically acceptable salts of such compounds; and to the use of such compounds as medicaments; especially as orexin receptor antagonists.