Total synthesis of rubriflordilactone B and pseudo-rubriflordilactone B

Rubriflordilactones B is a highly oxygenated nortriterpenoid natural product first isolated from Schisandra rubriflora in the year 2006. This natural product is of considerable interest due to its highly oxygenated polycyclic structure and significant anti-HIV activity. However, since the spectral data of the synthetically made natural product doesn’t match the isolated natural product, there is an ambiguity regarding the exact structure of the molecule. This thesis attempts to resolves the uncertainty around the structural motifs by synthesising both rubriflordilactone B and pseudo-rubriflordilactone B; the proposed compound responsible for the spectra in the isolation report. A highly convergent strategy for the synthesis of the natural product rubriflordilactone B and pseudo-rubriflordilactone B is described hereafter. A common AB ring aldehyde is involved in the late stage coupling with the diynes containing the FG rings of the rubriflordilactone B as well as pseudo-rubriflordilactone B. The coupling is followed by a rhodium-catalysed [2+2+2] cyclotrimerisation reaction to form the ABCDEFG core of the natural product skeleton which is only a step away from the completion.