Total synthesis of (–)-rhynchine A, (+)-rhynchine C and (+)-rhynchine E

Abstract

The first enantioselective total synthesis of (–)-rhynchine A, (+)-rhynchine C and (+)-rhynchine E has been successfully achieved in 11 steps via a convergent strategy. This efficient synthetic strategy provides 54 mg, 81 mg and 539 mg quantities of the above natural products at once, respectively, and revolves around three crucial transformations: firstly, substrate-controlled stereoselective ethylation and Michael addition are employed for the swift synthesis of the chiral proline fragment. Secondly, a mild Friedel–Crafts acylation is utilized for the formation of the tetracyclic skeleton. Lastly, a one-pot hydroxymethylation/oxidative cyclization method is employed for the construction of the tetrahydrofuran ring.