Ines Mancini et al. previously discovered that the configuration of C6 in the highly functionalized eunicellanes substantially influences conformational flipping, with (6Z) Δ 6,7 being a less strained and more stable version. However, the (6E) Δ 6,7 version displays broadening NMR signals and is prone to spontaneous conversion into a methoxy derivative in methanol. This observation aligns with our discovery and proposed principles, as cis configuration results in a less strained structure despite targeting different carbons. However, our findings contradict their discovery in a specific aspect as non-flexible microeunicellene (1) has (6E) Δ , suggesting that our "trans-cis" principle governs the flexibility of the carbon skeleton of eunicellane rather than their downstream functionalized counterparts.