Efficient Construction of the Kedarcidin Chromophore Ansamacrolide
摘要:
The streamlined assembly of the ansamacrolide framework of the kedarcidin chromophore via an efficient atropselective Sonogashira coupling step is described. To this end, two newly improved practical syntheses of the cyclopentene and diyne fragments have been developed, which feature 0.2 mol % catalytic loadings for an RCM step and 1-PrMgCl/CH(2)l(2) as a new entry to gem-disubstituted epoxides from ketones. both being applicable to 49-g scales.
Efficient Construction of the Kedarcidin Chromophore Ansamacrolide
摘要:
The streamlined assembly of the ansamacrolide framework of the kedarcidin chromophore via an efficient atropselective Sonogashira coupling step is described. To this end, two newly improved practical syntheses of the cyclopentene and diyne fragments have been developed, which feature 0.2 mol % catalytic loadings for an RCM step and 1-PrMgCl/CH(2)l(2) as a new entry to gem-disubstituted epoxides from ketones. both being applicable to 49-g scales.
Strong support for the recently proposed structure of the kedarcidin chromophore has been obtained through the convergent synthesis of the aglycon. The key features of the synthesis are an efficient assembly of the four fragments, a novel strategy involving an alkynyl epoxide, a cerium amide promoted nine‐membered diyne ring cyclization, and a SmI2‐mediated reductive 1,2‐elimination. TBS=tert‐butyldimethylsilyl
An efficient route to the neocarzinostatin chromophore aglycon has been developed. The present strategy involves a stereoselective intramolecular acetylide−aldehyde cyclization to form the C5−C6 bond, followed by efficient installation of α-epoxide, naphthoate, and carbonate functionalities. The C8−C9-olefin was introduced by using the Martin sulfurane dehydration reaction to furnish the highly reactive