cis–trans Isomerization of silybins A and B

• Michaela Novotná,
• Radek Gažák,
• David Biedermann,
• Florent Di Meo,
• Petr Marhol,
• Marek Kuzma,
• Lucie Bednárová,
• Kateřina Fuksová,
• Patrick Trouillas and
• Vladimír Křen

Beilstein J. Org. Chem. 2014, 10, 1047–1063, doi:10.3762/bjoc.10.105

• optically pure compounds was determined by using NMR and comparing their electronic circular dichroism data with model compounds of known absolute configurations. Mechanisms for cis–trans-isomerization of silybin are proposed and supported by quantum mechanical calculations. Keywords: 2,3-cis-silybin

• the 10,11-cis-isomer with the 2R,3R configuration was not observed during/after the isomerization of 1a in EtOAc. All the reactions in EtOAc were accompanied by C-23 O-acetylation. Separation and purification of 2,3-cis-silybins The separation of 2,3-cis-silybin 7 from unreacted 2,3-trans-silybin 1a