Total synthesis of (−)-ephedradine A: an efficient construction of optically active dihydrobenzofuran-ring via C–H insertion reaction

Functionalisation of Macroheterocycles with Preserving and Changing Their Sizes

“…In synthesis [83,84] of the complex macrocyclic spermine alkaloid (-)-ephedradine A (123) that is one of the hypotensive components of the traditional Chinese drug Mao-con, the closure of the 16-membered ring of polyamine (124) was also carried out under Mitsunobu conditions, and construction of the 13-membered ring of macro-lactam (125) included cyclization of precursor (126) with an activated ester group using the Staudinger/intramolecular aza-Wittig reaction (Scheme 29).…”

Five‐Membered Heterocycles: Benzofuran and Related Systems

“…As shown in Scheme 7.15, the optically active dihydrobenzo [b]furan-ring 48 has been constructed efficiently via a CÀH insertion reaction, leading to the total synthesis of (À)-ephedradine A [29].…”

Asymmetric Synthesis through C–H Activation

“…The formation of dihydrobenzofurans has been shown to be an applicable technology in total synthesis [196,197] . The key step in the total synthesis of ( − ) -ephedradine A ( 94 , Scheme 4.18 ) is the formation of trans -2 -aryl -2,3 -dihydrobenzofuran -3 -carboxylic acid ester 93 , which was synthesized from 92 via an Rh 2 ( S -DOSP) 4 -catalyzed, diastereoselective intramolecular C -H insertion.…”