| Fatigue is a physiological phenomenon that inevitably occurs when mental or physical strength reaches a certain stage.This is a subjective physical discomfort.Long-term overload work pressure will inevitably lead to the occurrence of fatigue symptoms,so that the various physiological functions of the body cannot maintain a normal state.With the accelerated pace of human life,fatigue has become more and more common,and more and more people are in a sub-health state.Anti-fatigue drugs are effective measures to relieve and eliminate fatigue.At present,the drugs with anti-fatigue activity mainly include Rhodiola rosea,American ginseng,benzedrine,methylphenidate,caffeine,etc.,which have the disadvantages of long course of treatment and many adverse reactions.Therefore,the development of new,efficient and safe anti-fatigue drugs is of great significance in military medicine.The wake-promoting drug modafinil has a structure of a racemate of diphenylmethyl sulfoxide acetamide,and has a certain anti-fatigue activity without obvious adverse reactions,but its anti-fatigue activity is weak.In this paper,a series of new compounds were designed and synthesized with modafinil as the lead compound.Molecules with significant anti-fatigue activity were found,and the structure-activity relationship law was revealed,which provided an important experimental reference for further research.Discovery of effective and safe anti-fatigue drugs.The main work completed includes:（1）Design and synthesis of diphenylmethyl sulfoxide acetamide compoundsThe results showed that the essential functional groups of modafinil and its analogues may be diphenylmethyl sulfolide acetamide structure,and some compounds still have good arousal activity after introducing different substituents on amide nitrogen atom.At present,there are few reports on the anti-fatigue activity of modafinil and its analogues.In this paper,the molecular structure modification strategy of modafinil is referred to in the literature.The anti-fatigue active molecule was designed and synthesized with modafinil as lead compound.The specific design idea is to retain pharmacophore and introduce different chain alkyl groups and ring alkyl groups into amide nitrogen.Chain alkyl substitution reflects the change of chain length and can be divided into monosubstitution and double substitution,while ring alkyl reflects the change of ring size and the presence or absence of heteroatoms,so as to investigate the influence of structural change on fatigue activity.Because the sulfur atom of sulfoxide is the chiral center,the designed compounds can be classified into racemic and chiral compounds.Ten racemic compounds C1-10 were prepared by condensation with amine and oxidation with 30%H2O2 using diphenyl-thio-acetic acid as starting material.It was separated into R-modafinic acid and S-modafinic acid by the separation reagent.Twenty chiral compounds R/S-C1-10 were prepared by condensation reaction with amines.The structures of 30 compounds were confirmed by 1H-NMR,13C-NMR and HRMS.（2）Study on asymmetric synthesis of R-target compoundsR-modafinil has a longer acting time,and its asymmetric synthesis method is of great significance.The representative method is obtained from the asymmetric oxidation of diphenylmethylthiyl acetamide.In this paper,the asymmetric oxidation synthesis method was optimized and applied to the asymmetric synthesis of R-diphenyl methyl sulfoxide acetamide.Firstly,the asymmetric oxidation of diethyl tartrate and isopropyl titanate was carried out,and the synthesis effect of ethyl acetate and solvent-free condition was investigated.Chiral high performance liquid chromatography（HPLC）normalization method was used to determine and calculate the enantiomer composition of target compounds.The optimized asymmetric oxidation synthesis of R-modafinil under solvent-free condition,chemical yield of 64.6%,ee:98.3%.It has good enantioselectivity,mild reaction conditions and friendly environment,which meets the requirements of green chemistry.Further optimization is expected to realize large-scale and commercial production.This method was applied to the asymmetric synthesis of R-diphenyl methyl sulfoxide acetamide.Using diphenyl-thio-acetic acid as starting material,diphenyl-thio-acetamide compounds were prepared by condensation with different amines.Then,asymmetric oxidation catalytic system of R-modafinil was used to compare the effect of oxidation of R-configuration target compounds under ethyl acetate and solvent-free conditions.The enantiomer composition of the target compound was determined and calculated by chiral high performance liquid chromatography（HPLC）normalization method.The chemical yield of ethyl acetate was41.0%～82.0%,ee was 44.0%～98.0%.The chemical yield was 58.0%～89.0%and ee was 22.0%～92.0%with solvent-free.The results show that the substituents on the amide nitrogen of the substrate have great influence on the chemical yield and chiral purity of the reaction when the method was used for asymmetric oxidation of diphenylmethyl thioacetamide substrates.The general rule is that the contribution of chain alkyl single substitution to the index is significantly higher than that of chain alkyl double substitution or cyclic alkyl.The longer the chain or ring of the substituent,the index shows a downward trend,and the index increases when the cyclic alkyl contains heteroatoms.The mechanism of this result may be that the greater the steric hindrance of the substituent on amide nitrogen,the stronger the power supply effect,the worse the result.（3）Anti-fatigue activity evaluation and structure-activity relationship analysis of target compoundsFirstly,the anti-fatigue activity of 30 target compounds was evaluated by a mouse rotating rod fatigue experimental model,with modafinil and R-modafinil as positive control drugs by a single intragastric administration of 0.2 mmol/kg.In the experiment,the compound had no significant effect on the body mass of the mice.Compared with the blank control group,modafinil,racemic compounds C1,C3,C5 and C8 could significantly prolong the residence time of mice on the rod（P<0.01）,and the result of C1 was superior than that of modafinil（P<0.01）;compared with the blank control group,R-modafinil,chiral compounds R-C1,R-C4,R-C4,R-C5,S-C5,R-C8,S-C8 and R-C10 could significantly prolong the residence time of mice on the rod（P<0.01）,and the results of R-C5,S-C5,R-C8,S-C8 and R-C10 were superior than that of R-modafinil（P<0.01）.Then,eight chiral compounds R-C1,R-C4,S-C4,R-C5,S-C5,R-C8,S-C8 and R-C10with good activity were screened out in the rotating rod experiment.The biochemical indexes of mice after exercise were determined.R-modafinil was used as the positive control drug,and 0.2 mmol/kg was administered by gavage once a day for 7 days.The contents of blood lactic acid and blood urea nitrogen in mice after continuous rod rotation exercise for 20 minutes were measured by enzyme labeling instrument to evaluate the effect of the compound on the changes of biochemical indexes and further evaluate its anti-fatigue activity.The results showed that compared with the model group,R-C1,R-C4,S-C4,R-C5,S-C5,R-C8,S-C8 and R-C10 could inhibit the increase of blood lactic acid and urea nitrogen levels in fatigue mice.Among them,S-C5,R-C8,S-C8 and R-C10 had superior effects on blood lactic acid levels than R-modafinil（P<0.01）,and S-C4 had superior effects on blood lactic acid levels than R-modafinil（P<0.05）.The effect of R-C5,S-C5,R-C8 and R-C10 on blood urea nitrogen level of mice was superior than that of R-modafinil（P<0.01）,and the effect of S-C8 on blood urea nitrogen level of mice was superior than that of R-modafinil（P<0.05）.Preliminary structure-activity relationship analysis showed that some racemates showed anti-fatigue activity after introducing chain alkyl or cycloalkyl groups into the amide nitrogen of modafinil.For chiral compounds,chain diethyl,n-propyl,di-n-propyl,diisopropyl and morpholine rings were introduced into the amide nitrogen of modafinil,and the compounds showed high anti-fatigue activity.Among them,the activity of di-n-propyl,diisopropyl and morpholine ring is stronger than that of R-modafinil.It is speculated that the introduction of an appropriate alkyl group into diphenylmethyl sulfoxide acetamide nitrogen can retain the anti-fatigue activity.There is no obvious difference between chain and cyclic alkyl groups.Double chain substitution is more favorable than single chain substitution.Chain alkyl and morpholine with a length of 3carbon are more beneficial to the anti-fatigue activity.In summary,30 target compounds of diphenylmethy lsulfoxide acetamide were designed and synthesized using modafinil as the lead compound in this project,among which 27 compounds have not been reported in literature.Four racemic compounds and eight chiral compounds showed significant antifatigue activity,C1 was superior than modafinil,and S-C5,R-C8,S-C8 and R-C10 were superior than R-modafinil.Preliminary structure-activity relationship analysis showed that the anti-fatigue activity could be retained by introducing appropriate alkyl substitution on diphenylmethylene sulphonyl acetamide nitrogen,and the anti-fatigue activity of alkyl chain and morpholine ring with a length of 3 carbon was more favorable.The asymmetric oxidation synthesis of R-diphenylmethyl sulphoxide acetamide compounds was optimized to achieve the solvent-free asymmetric oxidation synthesis of R-diphenylmethyl sulphoxide acetamide compounds including R-modafinil,and the product was purified by 75%ethanol recrystallization.The method has high yield,good enantiomer selectivity,mild conditions and meets the requirements of environmental protection.The application scope of this method was investigated,and the effects of amide nitrogen substitution enantiomer selectivity and reaction yield were summarized,which laid a foundation for further optimization and promotion of this method.The results of this study provide an important experimental reference for the further design and synthesis of these compounds,the study of anti-fatigue activity and the discovery of new anti-fatigue drugs. |
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