Total Synthesis and Configurational Validation of (+)-Violapyrone C

• Published in: European journal of organic chemistry Vol. 2014; no. 21; pp. 4472 - 4476
• Main Authors: Lee, Jong Seok, Shin, Junho, Shin, Hee Jae, Lee, Hwa-Sun, Lee, Yeon-Ju, Lee, Hyi-Seung, Won, Hoshik
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 01.07.2014; WILEY‐VCH Verlag; Wiley; Wiley Subscription Services, Inc
• Subjects: Chemistry; Chemistry, Organic; Gold; Natural products; Oxygen heterocycles; Physical Sciences; Science & Technology; Total synthesis; Wittig reactions; Gold; ACTIVATION; Oxygen heterocycles; Wittig reactions; HETEROCYCLES; Natural products; 3-SUBSTITUTED ISOCOUMARINS; DERIVATIVES; Total synthesis; CYCLIZATION
• ISSN: 1434-193X; 1099-0690
• DOI: 10.1002/ejoc.201402524

Gold(I)‐catalyzed intramolecular 6‐endo‐dig cyclization of tert‐butyl ynoates afforded α‐pyrone cores of violapyrones. Moreover, this reaction was successfully applied to the stereospecific syntheses of (+)‐ and (–)‐violapyrone C, which allowed the absolute configuration of natural (+)‐violapyrone C to be assigned by comparison of the optical rotations. This first total synthesis, which proceeded in 22 % yield over 10 steps from (S)‐(–)‐2‐methylbutanol, features silver(I) oxide promoted monobenzylation of 1,4‐butanediol, Wittig olefination, Claisen condensation, Corey–Fuchs reaction, and gold(I)‐catalyzed α‐pyrone synthesis. The total synthesis of (+)‐violapyrone C is accomplished through gold(I)‐catalyzed 6‐endo‐dig cyclization, silver(I) oxide promoted monobenzylation, Wittig olefination, and Corey–Fuchs reaction [22 % yield over 10 steps from readily available (S)‐(–)‐2‐methylbutanol]. The absolute configuration of natural (+)‐violapyrone C is determined; Tf = trifluoromethylsulfonyl.