Synthetic Studies Of Several Akuammiline Alkaloids And Palladium-catalyzed Coupling Reaction Of Arynes

The akuammiline alkaloids are a kind of bioactive alkaloids with complex structure,and the synthesis of two representative alkaloids strictamine and aspidophylline A were studied in this paper.In addition,the palladium-catalyzed coupling reaction of arynes was studied too.We decided to use the aryl radical C-H bond activation to construct the indole part in final phase after retrosynthetic analysis of strictamine which has a very rigid skeleton.After a large number of attempts,we constructed three key [3.3.1] bicyclo skeleton intermediates 3-55,3-60 and 3-75 with the efficient gold catalytic cyclization reaction start with compound 3-6.But we cannot to complete the synthesis the tricyclic skeleton whether we use reductive Heck reaction,Heck reaction,or other such as Michael addition reaction,radical cyclization reaction.Aspidophylline A is a bioactive alkaloid which has five continuous chiral centers in the all carbon six-membered ring.We synthesized the key intermediates 4-64 with the Wittig reaction start with the ?-ester aldehyde 4-37 after plenty of attempts.Then we obtained the tetracyclic compounds 4-71 and 4-77 after a series of nickel-mediated cyclization reactions,deprotection,semi-reduction and Pictet-Spengler cyclization reaction.But we failed to construct the last tetrahydrofuran ring.Aryne chemistry and allyl palladium chemistry are the hot spots in organic chemistry,and the combination of them is very promising.The cis-5,5a,6,10b-tetrahydroindeno[2,1-b]indoles were generated with vinyl benzoxazinanones and aryne precursors under fluorine reagents and palladium catalyst condition.It may involve the process of an unusual intramolecular nuclear reagent attacking the intermediate carbon of allyl palladium.And it may be also the first example that aryne inserted into the palladacyclobutane intermediate.