Krishnadimer A, an Axially Chiral Non-biaryl Natural Product: Discovery and Biomimetic Synthesis.

Krishnadimer A (1a), a C2-symmetric limonoid dimer representing a new class of axially chiral nonbiaryl natural products, was isolated and biomimetically semisynthesized by atroposelective 2,3-dichloro-5,6-dicyanobenzoquinone-mediated dienol-oxidative coupling. Single-crystal X-ray diffraction and electronic circular dichroism spectral analysis on the synthesized 1a unambiguously established its absolute configuration, including the P-configuration of the C15-C15' central axis. Antitumor investigations of the synthesized dimers 1a, 2a, and 2b revealed the large impact of axial chirality on bioactivities.