| Popis: |
Total synthesis of the title compounds is described. The key intermediate, dehydro-pentacyclic 13, is prepared in a sequence involving Pictet-Spengler reaction and DDQ oxidation. The key step in the synthesis was the dihydroxylation of 13 to afford the cis -diol 54, which was performed by direct oxidation with osmium tetroxide, whereas treatment of 13 with N-bromo-succinimide provided the trans -diol 41. Subsequent selective prenylation of 41 and 54 gave 13-epi-fumitremorgin B (45) and fumitremorgin B (1), respectively. 13-Epi-compound 45 is also converted into fumitremorgin B (1) by oxidation followed by reduction. |
