The Design,Synthesis And Anti-ad Activity Evaluation Of Novel GSK-3? Inhibitors

Alzheimer's disease(AD),an irreversible progressive neurodegenerative disorder mainly occurring in the elderly,is characterized by the presence of extracellular neuritic senile plaques(SP)and the intracellular neurofibrillary tangle(NFTs).The SP and NFTs were formed by the deposition of A? and hyperphosphorylated tau proteins respectively.Although the etiology and pathogenesis were complicated and correlated,a series of hypotheses are proposed to explain the causes of AD,including the main amyloid cascade hypothesis and the hyperphosphorylated tau hypothesis,as well as the cholinergic hypothesis,the inflammation hypothesis,the oxidative stress hypothesis and the metal ion dyshomeostasis hypothesis.The current FDA-approved therapies are cholinesterase inhibitors(tacrine,donepezil,galantamine and rivastigmine)and an NMDA receptor antagonist(memantine)that provide only modest symptomatic relief in memory and cognitive defects,but can not reverse the process of AD.With the acceleration of population aging,the number of AD patients increases quickly.The limited therapeutic efficacy cannot satisfy the present clinical demand.Therefore,the development of effective anti-AD drugs has become an urgent need for the medicinal chemists.In view of the complicate and multifacet pathogenesis of AD,the molecule targeting one facet of AD is not very effective.Therefore,the developments of the multi-targeted anti-AD drugs,especially those with multiple action mechanisms and targeting multiple pathological processes of AD becomes the main concerns.GSK-3? is a proline-directed serine/threonine kinase.It is a key molecule that links A?,tau,inflammation,synapse and neuron,and plays a vital role in the pathological process of AD.The activated GSK-3? hyperphosphorylates the tau proteins,that impairs the interaction between tau proteins and microtubules,leading to the disjunction of tau proteins from microtubules.The subsequent aggregation of hyperphosphorylated tau proteins results in the formation of neurofibrillary tangles(NFTs)and neuronal cell death.GSK-3? also promotes A? production by escalating the activity of ?-secretase(BACE1),a key enzyme for the A? formation.The increased A? inclines to form the SP.Moreover,the actived GSK-3? can also affect the release of neurotransmitters,promote inflammation and induce cell apoptosis.Therefore,GSK-3? has become one of the key targets for the anti-AD drug development.The purpose of this study is aimed to discover novel GSK-3? inhibitors,and the main contents are divided into the following four parts:Part 1.To discovery novel multifunctional GSK-3? inhibitors with the antioxidative stress ability and targeting the AD metal dyshomeostasis,we used the pyrrolopyridinone GSK-3? inhibitors as a lead structure,kept the pyridinamide fragments to maintain the interaction with GSK-3? in the hinge region,replaced the pyrrolopyridinone core with the metal chelating activities of 2,3-diaminopyridine ring that has the metal chelating ability,and connected the two pyridine rings with an amide or an imine or a CH2NH bridge,designed the 2,3-diaminopyridine GSK-3?inhibitors targeting the multi-facets of AD.The condensation of 2(cyclopropanecarboxamido)isonicotinic acid with substituted 2,3-diaminopyridine afforded the amide series compounds;Reaction of the 2(cyclopropanecarboxamido)isonicotinaldehyde with substituted 2,3-diaminopyridine derivatives provided the imines;The reduction of imines with NaBH4 generated the 1,2-diamine derivatives.The amide derivatives A01-A06 showed moderate potency against GSK-3? with weak Cu2+,Zn2+ and Al3+ chelating ability.The imine derivatives A07,A08 and All were potent GSK-3? inhibitors(IC50=38-71 nM)and had selective Cu2+ and Al3+ chelating ability.The 1,2-diamine derivatives A18-A22 were strong metal-chelators,but decreased or lost their GSK-3? inhibitory potency.In vitro,compounds A07,A08 and All,especially A08,exhibited good ROS inhibitory and antioxidant activities,potently inhibited the Cu2+-induced A? aggregation and promoted the Cu2+-A? complex disaggregation.In cell level,compounds A07,A08 and All can inhibit tau protein phosphorylation and protect neuro cells from Cu2+A?1-42 and H2O2-induced cell damage.Furthermore,compound A08 was predicted to have the ability to pass the BBB with drug likeness properties.Through this study,a novel multifunctional GSK-3? inhibitor A08 that has the anti-oxidative stress ability and targets the AD metal dyshomeostasis was first discovered.Part 2.Based on the binding modes and features of the pyridine-pyrrole GSK-3?inhibitors,through the introduction the metal chelating fragments at the ? interation region and using different linker to connect the aromatic groups to occupy the ?interation zone,we designed a series of novel pyridine-pyrrole GSK-3? inhibitors to target multfacets of AD.The o-hydroxyacetophenone portion was first introduced through the the Suzuki coupling with the benzenesulfonyl protected 5-bromo-3iodine-7-azacindole.After the removal of the benzenesulfonyl protective group,the linker and the ? region binding motifs were further connected at the 5-position of the pyridine-pyrrole core through the Suzuki coupling to build the compounds B01-B05.Applying the same synthetic strategy and through a series of chemical transformations,the pyridine-pyrrole derivatives B06-B10 were prepared.Compounds B01-B09 had no or low inhibitory activity against GSK-3? at the concentration of 1 ?M.However,compound B05 showed selective Cu2+ and Al3+ chelating ability,and could inhibit the Cu2+-induced A? aggregation and promote the Cu2+-A? complex disaggregation.The 8-hydroxyquinoline derivative B10 was potent GSK-3? inhibitor with an inhibitory rate of 89.7%at 1 ?M.B10 was selective Fe2+,Zn2+,Cu2+ and Al3+ chelator and free radical scavenger.More important,B10 can directly act on A?1-42,significantly inhibit the A?1-42 aggregation and promote the disaggregation of A?1-42 complex.Moreover,B10 can effectively inhibit Cu2+-induced A?1-42 aggregation and accelerate the disaggregation of Cu2+-A?1-42 complex.Therefore,in this study,we first discovered a novel GSK-3? inhibitor(B10)that has a direct act on A?,and has the anti-oxidative stress ability and can target the AD metal dyshomeostasis.Part 3.In order to find efficient GSK-3? inhibitors,a strategy to enhance the hydrogen bindings with the GSK-3? hinge region was adopted in the design of pyridine-pyrazole derivatives as novel GSK-3? inhibitors.The 3-aminopyrazole motif was used as the hinge binding group and expected to form multiple hydrogen bonds with ASP133,TYR134 and VAL135.The condensation of 2-chloro-5-bromonitrile with hydrazine hydrate afforded the bromo-substituted pyridine-pyrazolamine core.After the butylsulfonylation of the amino group,the 3-pyridine or substituted 3pyridine,and o-hydroxyacetophenone portion were introduced through the Suzuki coupling to generate the pyridine-pyrazole derivatives C01-C10.At the concentration of 1 ?M,C01-C10 showed weak GSK-3? inhibitory activity with the inhibition rate less than 50%.Compounds C05,C06 and C07 showed moderate Cu2+chelating ability,weak Cu2+-A? complex disaggregation and no Cu2+-induced A? aggregation inhibitory activity.Part 4.To further verify the design concept of enhancing the hydrogen bindings with the GSK-3? hinge regio,a novel thiophene-pyrazole derivatives were designed using 3-aminopyrazole as the hinge binding motif.After the protection of thiophenopyrazolamine with Boc groups,the bromo was introduced at the 5-position.After the removal of the Boc protective groups,the 4-acetyl-3-hhydroxyphenyl,3pyridyl or aryl substituted 3-pyridyl were introduced at the thiophene-pyrazole 5postion to build up compounds D01-D08.Ten compounds of E series,containing NC-C-N or N-C-C-O chelating motifs,were prepared using the same synthetic strategy.Compounds D01-D08 showed potent GSK-3? inhibitory activity,especially D01,D03 and D05,with IC50 values of 36,37 and 31 nM,respectively.Moreover,D01,D03 and D05 had selective metal ions chelating ability,some Cu2+-induced A?aggregation inhibitory and Cu2+A? complex disaggregation activity.However,compounds E01-E10 were weak GSK-3? inhibitors.E02,E08 and E10 showed some metal ions chelating abilty,and had some effects on the Cu2+-induced A? aggregation and the Cu2+-A? complex disaggregation.In summary,to find multi-targeted anyi-AD drugs,we designed and synthesized a series of 2,3-diaminopyridines(A01-A22),pyridine-pyrroles(B01-B10),pyridinepyrazoles(C01-C10)and thiophene-pyrazoles(D01-D08;E01-E10)as novel GSK3? inhibitiors.The imine derivative A08 was the first potent GSK-3? inhibitor discovered that has the anti-oxidative stress ability and targets the AD metal dyshomeostasis.The pyridine-pyrrole derivative B10 was the first GSK-3? inhibitor that has a direct effect on A? aggregation and disaggregation,targets the AD metal dyshomeostasis as well as the AD oxidative stress.Therefore,B10 can act as a good drug lead for further structural modification and biological evaluations.The pyridinepyrazoles(C01-C10)and thiophene-pyrazoles(E01-E10)showed weak or no activity on GSK-3?,indicating the lacking of proximity in the inhibitor design.The thiophene-pyrazoles(D01-D08)showed potent GSK-3? inhibitory activity as well as some AD-related metal chelating ability,providing a structural basis for further modifications.