Total Synthesis of Ophiorrhine A, G and Ophiorrhiside E Featuring a Bioinspired Intramolecular Diels–Alder Cycloaddition**

(+)/(-)-Yanhusamides A-C, three pairs of unprecedented benzylisoquinoline-pyrrole hetero-dimeric alkaloid enantiomers from Corydalis yanhusuo

A chemical investigation on the aqueous extract of Corydalis yanhusuo tubers led to the isolation and structural elucidation of three pairs of trace enantiomeric hetero-dimeric alkaloids, (+)/(-)-yanhusamides A-C (1-3), featuring an unprecedented 3,8-diazatricylco[5.2.2.0^2,6]undecane-8,10-diene bridged system. Their structures were exhaustively characterized by X-ray diffraction, comprehensive spectroscopic data analysis, and computational methods. Guided by the hypothetical biosynthetic pathway for 1-3, a gram-scale biomimetic synthesis of (±)-1 was achieved in 3 steps using photoenolization/Diels-Alder (PEDA) [4+2] cycloaddition. Compounds 1‒3 exhibited potent inhibition of NO production induced by LPS in RAW264.7 macrophages. The in vivo assay showed that oral administration of 30 mg/kg of (±)-1 attenuated the severity of rat adjuvant-induced arthritis (AIA). Additionally, (±)-1 induced a dose-dependent antinociceptive effect in the acetic acid-induced mice writhing assay.

Divergent Total Syntheses of Hetero-Oligomeric Iridoid Glycosides

Divergent total syntheses of the hetero-oligomeric iridoid glycosides mainly found in Dipsacus asper were achieved. Thus, loganin (1), which is important as a monomer unit, was efficiently synthesized by stereoselective reductive cyclization using secologanin (2) as a substrate. Sequential condensation reactions of derivatives of 1 and 2 as monomer units led to the first enantioselective total syntheses of the heterooligomers cantleyoside, (E)-aldosecologanin, dipsaperine, (3R, 5S)-5-carboxyvincosidic acid 22-loganin ester, and dipsanoside A.