Synthetic Approaches to Crinipellin Based Tetraquinanes via Ring-Rearrangement Metathesis and Ring-Closing Metathesis

Herein, we have studied the synthetic approaches to tetraquinanes that are present in crinipellin type natural products by employing ring-rearrangement metathesis (RRM) and ring-closing metathesis (RCM) as key steps. These studies involve finding the suitable alkylation sequence to prepare desired RRM/RCM precursors. Methyl-tetraquinane has been assembled by employing a regio-, and stereoselective methylation followed by allylation sequence. Whereas, allyl-tetraquinane was constructed by following the allylation-RRM sequence. Interestingly, spiro-quinanes rearranges to fused-quinanes when olefinic moiety is present adjacent to the spiro-ring under RRM conditions. Additionally, several di-, and triquinane derivatives reported during this study were also found in diverse polyquinane natural products. The present strategy utilizes the vinyl derivative of exo-dicyclopentadiene-1-one, and produce several intricate polycyclic systems. Our strategy may be useful to design various medicinally important "drug-like" molecules.