Polycyclic structures fused at a central carbon are of great interest due to their appealing conformational features and their structural implications in biological systems. Although progress in the development of synthetic methodologies towards such structures has been impressive, the stereoselective construction of such quaternary stereocentres remains a significant challenge in the total synthesis of natural products. This review highlights the progress in the formation of 1-oxaspiro[4.n]alkan-2-ones (2≤n≤7) with concomitant formation of the quaternary spiro centre.

The stereoselective transformation of ketones to substituted olefins has become of great importance in organic synthesis. This Review helps to define the scope and limitations of the first-row transition metal-catalyzed cross-couplings between various enolates and aryl, heteroaryl, alkenyl, alkynyl, and alkyl Grignard and zinc reagents.

The BCD tricyclic core of brownin F was prepared in eight synthetic operations for the first time. Our synthesis features a diastereo-, chemo-and regioselective intramolecular [3 + 2] cycloaddition between a cyclic carbonyl ylide and a γ-alkylidenebutenolide.