On the Erosion of Enantiopurity of Rhodonoids via Their Asymmetric Total Synthesis.

Rhodonoid natural products are found in nature as a scalemic mixture. This interesting phytochemical feature is presumed to originate from a reversible electrocyclic ring opening of the chromene core present in the biogenetic precursors of rhodonoids. Herein, we systematically investigated factors that are responsible for this racemization event. This eventually led us to complete the asymmetric total synthesis of rhodonoids A, C, D, and G.

(+)-Dimericbiscognienyne A: Total Synthesis and Mechanistic Investigations of the Key Heterodimerization.

The first total synthesis of (+)-dimericbiscognienyne A is described. Key to the successful access to (+)-dimericbiscognienyne A was a biosynthetically inspired Diels-Alder reaction between two differential epoxyquinoid monomers and the subsequent intramolecular hemiacetal formation. The selective formation of the natural product among other possible diastereomers during the late-stage [4+2] cycloaddition reaction was investigated by DFT calculations and experimental control studies.