Study On The Synthesis Of Ester Balasubramide Derivatives And Their Photoaffinity Molecule Probes

(+)-（5S,6R）-balasubramide is an indole octamembered cyclolactam compound was isolated from the leaves of Clausena indica（Daztz）oliv.Our research group has completed the total synthesis of（+）-（5S,6R）-balasubramide and its preliminary structure-activity relationship in the early stage,and found that when the N-methyl was removed,4-trifluoromethylphenyl was used to replace the phenyl at position 6 of the eight membered lactam ring,and the hydroxyl at position 5 of the eight membered lactam ring was etherified or esterified,the series of derivatives have different biological activities such as antioxidation,nerve cell protection and anti-neuritis.Except for a few compounds,most compounds have less cytotoxicity,among them,the compounds（+）-（5S,6R）-ester balasubramide derivatives（+）-3C-20,that the phenyl was substituted by 4-trifluoromethylphenyl and the hydroxyl at position 5 was etherified with 3-（4-trifluoromethyl）phenylpropionic acid,has strong neuroprotective and anti-inflammatory activities.In order to find a lead compound with better biological activity,this thesis continues to modify the structure of this ester balasubramide.The structural modification of natural product（+）-（5S,6R）-balasubramide in the early stage of our research group mainly focused on the eight membered ring,leaving the indole ring unchanged,and failed to obtain an excellent lead compound.Because the action target protein of these compounds is not clear,the structural modification in this thesis can only be based on the principle of structural diversity in drug molecular design.For the purpose of changing the lipid water distribution coefficient lg P and the electron cloud density distribution on the aromatic ring,the structure of compound（+）-3C-20 is locally modified,and different substituents were introduced at different positions on the indole ring,8 new ester balasubramide derivatives were designed and synthesized,and their biological activities were preliminarily evaluated.Concurrently,in order to determine the anti-inflammatory target of this structural type compound,a（+）-3C-20 molecular probe labeled with aliphatic bisacridine photoaffinity group was designed and synthesized,which laid a first stone for the follow-up study of its target protein and action mechanism.Synthesis and preliminary biological activity evaluation of ester balasubramide derivatives:firstly,（+）-（2S,3R）-3-（4-（trifluoromethyl）phenyl）oxirane-2-carboxylic acid-α-phenyl-ethylamine（H2）was obtained from 4-trifluoromethylbenzaldehyde by Wittig reaction and asymmetric epoxidation.Then,substituted indole derivatives were used as raw materials,the key intermediate substituted tryptamine derivatives（T2a-h）were obtained through Friedel-Crafts acylation reaction,ammonolysis reaction,reduction reaction and hydrochloride formation reaction.N-acylation of T2a-h with H2 which was acidified with HCl gave the linear amide（+）-B1a-h respectively,and the final 8 new target compounds of（+）-B3a-h were obtained by successive intramolecular cyclization,O-acylation,the total yield of the seven-step reaction was 14.8～19.5%（based on substituted indoles derivatives）,the ee%of all target compounds reached more than 98%,and the synthesis process of the key intermediate H2 was optimized,which simplified the operation and was more suitable for batch preparation.Combined with the previous research results on the structure-activity relationship of these compounds,the preliminary neuroprotective and antioxidant effects of the synthesized target compounds were studied by MTT method.It was found that the compounds substituted by methoxy or benzyloxy at position 5 and methyl at position 7 on the indole ring have certain neuroprotective effects,and the compound with 7 methyl substitution on indole ring also have a certain antioxidant effect.Synthesis of photoaffinity molecular probe of ester balasubramide derivative:In the previous study on the structure-activity relationship of balasubramide,our research group found that some compounds have certain neuroprotective and anti-inflammatory effects,but their action targets are not clear.In order to clarify their molecular mechanism and provide design basis for further structural transformation of these compounds.In this thesis,a new photoaffinity probe molecule of ester balasubramide derivative was synthesized by introducing a photoaffinity probe molecule fragment at position 5 of indole nucleus of ester balasubramide compound.Referring to the existing literature and the existing synthesis methods of bisacridine photoaffinity probes in our research group,the photoaffinity probe 3-（3-alkynbutyl）-3H bisacridine acid（P4）was obtained from 4-pentynoic acid through four steps of condensation,alkylation,hydrolytic decarboxylation and carbonyldiazinization.Then,the above synthesized 5-benzyloxy substituted ester balasubramide derivative（+）-B3h was debenzylated to obtain 5-phenolic hydroxyl substituted ester balasubramide derivative（+）-B3-OH.After esterification with probe molecule P4,a new ester balasubramide probe molecule was obtained.This can lay a foundation for the follow-up study of the design and synthesis of new probe molecules of these compounds and the study of their neuroprotective targets.In this thesis,a total of 64 intermediates and target compounds were synthesized,including 26 unreported compounds.The structures of all new compounds were confirmed by ¹H NMR,¹³C NMR and HRMS.The enantiomeric excess values of all optically active intermediates and target compounds were determined by polysaccharide chiral columns Chiralpak OJ-H and Chiralpak AD-H,the enantiomeric excess values of all compounds were more than 98%.Other biological activities of the prepared derivatives and the search for neuroprotective targets by using the synthesized photoaffinity molecular probes are in progress.