ortho-Quinone Methide Cyclizations Inspired by the Busseihydroquinone Family of Natural Products

Abstract

A series of cascade reactions of o-quinone methides have been developed based on the proposed biosynthesis of busseihydroquinone and parvinaphthol meroterpenoid natural products. The polycyclic framework of the most complex family members, busseihydroquinone E and parvinaphthol C, was assembled by an intramolecular [4 + 2] cycloaddition of an electron-rich chromene substrate. The resultant cyclic enol ether underwent rearrangements under acidic or oxidative conditions, which led to a new total synthesis of rhodonoid D.

Elucidating the Mechanism of Metabolism of Cannabichromene by Human Cytochrome P450s

“… 32 In order to secure different oxidation products, several protocols were explored to obtain desired chemoselectivity. For example, allylic oxidation could be achieved selectively at the C-8′ position by directly subjecting CBC ( 1 ) to SeO 2 , 33 affording 8′-hydroxy-CBC ( 2 ) in appreciable yield. On the other hand, all other oxidations involving CBC required protection as noticeable degradations were observed when the free phenol was used.…”

Theoretical calculations of formation and reactivity of o -quinomethide derivatives of resorcin[4]arene with reference to empirical data

“…o-QMs containing an additional double-bond spontaneous transform via oxa-6π electrocyclization to 2Hbenzopyrans products. Expansive reactivity of the o-QM can be used in the reaction for the construction of various natural products [6][7][8].…”

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

“… Subsequently, the same research group isolated rhodonoids C–G ( 3–7 , respectively) from the same plant . The intriguingly fused structures of rhodonoid natural products immediately attracted the attention of the synthetic community, and elegant total syntheses were accomplished by George’s research team − and Tang and Hsung’s joint research team . Notably, both research teams utilized a biomimetic strategy that exploits the chemical reactivity of the chromene core in accessing the racemic mixture of the target compounds.…”

“…In that regard, the isolation of rhodonoids with an eroded ee caught our attention, especially with respect to their biogenesis. Previous synthetic studies − hinted that chromene derivative 8 is the biosynthetic precursor that undergoes diverse modes of (oxidative) cyclization to forge the distinct rhodonoid frameworks (Scheme ). We hypothesized that the erosion of ee during rhodonoid biosynthesis originates from the reversible electrocyclic ring opening of the chiral chromene core (Scheme ).…”