Synthetic Studies Of Aurantioclavine And Mycestericin E

Natural products bearing diverse chemical structures often have important physiological activities,which make them important source of drugs for the treatment of many diseases.In this paper,the indole alkaloid aurantioclavine and polyhydroxysphingosine-type natural products mycestericin E was selected as synthetic targets,and the chiral auxiliary groupinduced cyclization and nitroso-ene reaction were used as key strategies,respectively.The first part mainly focused on the total synthesis of indole alkaloid aurantioclavine.Using 4-bromotryptamine or 4-bromoindoleacetic acid as starting materials,different chiral auxiliaries and protective groups are introduced into the molecule,and then the allylic aminative cyclization is realized by the palladium-catalyzed Heck reaction.Unfortunately,the target product can not be obtained in the final removal of chiral auxiliary groups.Further optimization of this reaction is currently underway.In the second part,with mycestericin E as the target molecule,the nitroso-ene reaction was designed to introduce α-nitrogen-containing carbon stereogenic center,which constitutes an interesting selectivity resersal in the nitroso-ene reaction of the electron-deficient conjugated olefins,and completes the synthesis of α-quaternary carbon amino acids.The total synthesis of mycestericin E was enabled by Julia reaction to introduce the long chain and subsequent deprotection operations.This synthetic strategy provides an efficient approach toward other sphingosine natural products bearing α-nitrogen containing quaternal carbon chiral centers.In this study,it was also found that the stereoselectivity of the nitroso-ene reaction was related to the double bond configuration.It was speculated that diradical or azetidine oxide intermediates may be involved in the key nitroso-ene cyclization,and further mechanistic studies are underway.