Synthetic Strategies to Diverse Polyquinanes via Olefin Metathesis: Access to the Basic Core of Crinipellin, Presilphiperfolanol, and Cucumin

A rapid and useful synthetic approach to various polyquinane-based
natural products was accomplished efficiently by employing ring-rearrangement
metathesis and ring-closing metathesis as key steps. Here, we report
the synthesis of stereochemically well-defined cis-anti-cis triquinanes (1, 2), tetraquinanes (3, 4), a novel pentaquinane 5, and
fused [5-5-5-6] tetracyclic systems (6, 7) that are present in crinipellin, presilphiperfolanol, cucumin,
etc. Hence, the current strategy may be suitable for the synthesis
of various complex natural and unnatural cyclopentanoid targets. Moreover,
our approach to the newly synthesized pentaquinane 5 has
paved the way for various complex polyquinanes/molecules having significant
applications in theoretical and medicinal chemistry.