Synthesis And Bioactivities Of Erythromycin Derivatives

Erythromycin,a typical macrolide antibiotic,had been extensively used in the clinic for more than 50 years.In addition to the anti-microbial effects,many clinical studies suggested that erythromycin and its derivatives had some other activities,such as prokinetic activity, anti-inflammatory activity,luteinizing hormone-releasing hormone antagonistic activity and phosphodiesterase-3 inhibitory activity.Moreover,they had been discovered to have a beneficial effect on the treatment of tumor.Although there were some reports in the past few years of macrolide antibiotics having helpful effects on antitumor treatment,to the best of our knowledge,the inhibitory activity of erythromycin derivatives on the proliferation of tumor cells had never been reported.Up to now, little attention had been paid searching for the novel erythromycin derivatives with antitumor activity.In this article,preliminary investigations are made in this field.In our study of "Synthesis & Bioactivities of Erythromycin Derivatives",a new class of erythromycin derivative,dimmer of erythromycin was discovered and after further investigation, it was found to show in vitro antitumor activity.Therefore it was picked as the lead compound and through the change of the connecting chain and the connecting nodes on erythromycin derivatives,two kinds of dimmers of erythromycin derivatives（"tail to tail" dimmers,TTD and "head to head" dimmers,HHD）were designed and synthesized at first;then by the removal of one of the macrolactone ring from the dimmers of erythromycin derivatives,two kinds of simplified analogues of macrolide dimmers,"tail variation" monomer（TM）and "head variation" monomer（HM）,were designed and synthesized.Totally,73 novel erythromycin derivatives were synthesized for the in vitro antitumor activity test.During the synthesis of intermediate,the cladinose moieties of erythromycin derivatives could be selectively removed upon the treatment with dilute hydrochloric acid in an aqueous solution;employing NaBH₄ as a reducing agent in methanol,9（S）-hydroxyl erythromycin derivatives could be prepared conveniently;N-demethylated erythromycin derivatives were obtained by N-demethylation with iodine and sodium acetate in methanol;The synthesis of 12-membered ring erythromycin derivatives（containing a acetyl side chain）and its N-monodemethyled product were accomplished by the use of lead tetraacetate as an oxygenant; 9（S）-Erythromycylamin was synthesized by selective reduction of erythromycin A 9（E）-oxime with NaBH₄/ZrCl₄ under ultrasonic irradiation.The synthesis of the "tail to tail" dimmers（BK-01～BK-39,TTD）was accomplished through the alkylation or acylation of the N-demethylated erythromycin derivatives."Head to head" dimmers（BK-40～BK-48,HHD）were prepared from the 9（E）-oxime erythromycin derivatives,by the use of（E）-1,4-dibromo-2-butene as the alkylating agents.Using N-demethylated erythromycin derivatives and nitrogen-containing heterocycles as the substrates, 1,3-bromochloropropane,（E）-1,4-dibromo-2-butene and chloroacetyl chloride as the alkylating or acylating agents,"tail variation" monomers（BK-49～BK-60,TM）were prepared."Head variation" monomers（BK-61～BK-73,HM）were prepared by utilizing 9（E）-oxime erythromycin derivatives and nitrogen-containing heterocycles as the substrates,（E）-1,4-dibromo-2-butene as the alkylating agents.All the target compounds and intermediates were characterized by the applications of MS, ¹H NMR and ¹³C NMR.The data of ¹³C-NMR spectra were discussed briefly.54 of the target compounds were evaluated for their in vitro antitumor activities against human SGC-7901,KB,HT-1080 and HL-60 cell lines by MTT assay or Trypan blue staining. And the structure-activity relationships study of them was also performed initially.The in vitro antitumor activity of "tail to tail" dimmers（TTD）and "head to head" dimmers （HHD）was firmly established by our assay.4-HHD and 4-TTD showed potent antitumor activity and the IC₅₀values of some erythromycin derivatives were between 0.1 and 1.0μM.In addition,both "tail variation" monomers（TM）and "head variation" monomers（HM）were shown to be active in the assay.Some of the HM were found to retain much of the activity of their parent compounds（4-HHD）,with an IC₅₀of 0.1-1.0μM.Compared to HM,TM 1ed to the decrease of antitumor activity.BK-23（4-TTD）and BK-63（HM）induced apoptosis in human SGC- 7901 or HL-60 cell lines and their influence on cell cycle were detected by flow cytometry performed by PI staining. Flow cytometry suggested that the dimmers of erythromycin derivatives BK-23 and the simplified analogue BK-63 could induce apoptosis which revealed that they may have a similar mechanism.Erythromycin derivatives containing different structures could induce apoptosis in a dose-dependent fashion and the mechanism of the antitumor activity of erythromycin derivatives highly correlated with the induction of apoptosis.We also focused our attention on the synthesis of erythromycin derivatives and related reactions.For the first time,we developed two methods to prepare the ring-contracted erythromycin derivatives via microwave-assisted intramolecular transesterification under either solvent-containing or solvent-free conditions.In addition,we found a novel water soluble sodium acetate-doped calcium chloride system to be used as the solid support in the microwave-assisted reactions and developed a new,straightforward synthesis of ring-contracted erythromycin derivatives by one-pot reaction of erythromycin and its derivatives via intramolecular dehydration and transesterification.Furthermore,we found a novel N-formylation and related reactions via umpolung of cyanide ion promoted by esters and developed a new,general method for the synthesis of formamides,N,N’-disubstituted formamidines,benzoimidazole,N-（aminomethylene）malonate and its derivatives.