Catalytic Asymmetric Synthesis of Inherently Chiral Eight-Membered O-Heterocycles through Cross-[4+4] Cycloaddition of Quinone Methides.

Inherently chiral eight-membered rings embedded in tetraphenylene derivatives and hetero-analogues exhibit unique properties and allow diverse applications. A conceptually viable and straightforward approach to these frameworks is [4+4] cycloaddition, which still remains elusive. Herein, we describe the stereoselective cross-[4+4] cycloaddition of quinone methides (QMs), leading to the formation of oxa-analogues of tetraphenylene with exceptional chemo-, diastereo-, and enantioselectivity.

Isolation, structural and bioactivities of polysaccharides from Anoectochilus roxburghii (Wall.) Lindl.: A review.

Anoectochilus roxburghii (Wall.) Lindl. (A.