Study On Structural Optimization Of Chiral Ionone Alkaloid Derivative ION-31a And Anti-tumor Metastatic Activity

Objective:The previous investigations in our laboratory have found that the chiral ionone alkaloid derivative ION-31a showed significant anti-metastatic activity against breast cancer cells.Based on this lead compound,the tertiary amine group of ION-31a was structurally modified,and was carried out skeleton modification to replace chiral carbon,chiral ionone alkaloid derivatives and other alkaloid derivatives were synthesized.This paper deals with the anti-metastatic activities and structure-activity relationship of alkaloid derivatives,in the hope of discovering more derivatives with better activity.Methods:Chiral ionone alkaloid derivatives with different structures were designed using medicinal chemistry methods.The chiralα-ionone was obtained by lipase resolution and used as starting reagent.The chiral ionone alkaloid derivatives were prepared by haloform reaction,amidation reaction,catalytic hydrogenation reaction,amide reduction reaction,amino protection and de-protection reaction,allylic oxidation,reductive amination,bromination reaction,Suzuki coupling reaction and nucleophilic substitution reaction.Moerover,based on the structure-activity relationship of chiral ionone alkaloid derivative,a series of other alkaloid derivatives were synthesized using achiral strucutre as starting reagent.The chemical structures of all target compounds have been characterized using nuclear magnetic resonance spectroscopy and high-resolution mass spectrometry.The structure-activity relationship of the derivatives was studied based on their anti-metastatic activities,which were evaluated through chemotaxisc migration assay of breast cancer cells.Results:1.In this paper,one hundred and fifty-five compounds,including sixty seven intermediates and eighty eight derivatives,were synthesized by organic chemistry reactions.All of the compounds were characterized by organic spectroscopic methods.All the synthesized derivatives were novel compounds which had not been reported before.2.The MTT assay was used for evaluation of the cytotoxicity of 88 alkaloid derivatives,and the results showed that the target derivatives had no cytotoxicity in the concentrations ranging from 0.25 to 50mM.The derivatives were screened by invasion assay using MDA-MB-231 breast cancer cells under non-cytotoxic concentrations.The results showed that compounds N2,N5,N7,N8,N10,N18,N25,N26,N37,N38,N43 and N71 revealed significant anti-metastatic activity,and their IC₅₀values were ranging from 0.035 to 1.096mM.Among them,derivative N18 was found to be of strong activity(IC₅₀=0.035mM)and therefore,worth further investigation.3.The structure-activity relationship study on the chiral ionone alkaloid derivatives had indicated that the tertiary amine substituent groups and their degrees of freedom in rotation could significantly affect the anti-metastatic activities.When benzonitrile substiuent group was existed,the activities of derivatives were significantly improved.If biphenyl fragment was introduced into derivatives,the activities of derivatives were reduced due to the rigidity of benzene rings and the decreased number of rotatable bonds in the molecule.The conformation-limiting derivatives of tertiary amine part were essentially inactive,which suggested that the chain tertiary amine group had an important effect on the activities of the compounds.4.The relationship between biological activity and 4 common drug-likeness（c Log P,t PSA,the number of hydrogen bond receptor and the number of rotatable bond）was investigated.Among these,there was a certain degree of correlation between the c Log P,t PSA,rotatable bonds number and the activity of compounds.Among the componds whose inhibition rate on tumor metastasis were greater than 70%at a concentration of 10μM,most of them were modified derivatives of N-methyl structural fragment.The c Log P was concentrated in the range of 5.5-7.0,t PSA was concentrated in the range of 25.0-55.0,and the number of rotatable bonds was mostly8-10.This result could provide an important theoretical basis for later structural optimization.Conclusion:In this paper,a total of eighty eight chiral ionone alkaloid derivatives and other alkaloid derivatives were prepared through multi-step organic synthesis reactions.These were all novel compounds that were not reported in the literature.Compounds N2,N5,N7,N8,N10,N18,N25,N26,N37,N38,N43 and N71exhibited significant inhibitory effects on the invasion of human MDA-MB-231breast cancer cells.The structure-activity relationship indicated that the chain tertiary amine group exerted an important role in the anti-metastatic activity.Moreover,the existence of benzonitrile substiuent group could significantly improve the activities of derivatives.