Cyclohexane-Fused Octahydroquinolizine Alkaloids from Myrioneuron faberi with Activity against Hepatitis C Virus

Investigation of the alkaloids from Myrioneuron faberi, a plant unique to China, gave
four pairs of enantiomers (1–4).
(±)-β-Myrifabral A (1) and (±)-α-myrifabral
A (2) formed an inseparable mixture of anomers (cluster
A), as did (±)-β-myrifabral B (3) and (±)-α-myrifabral
B (4) (cluster B). Their structures were determined by
X-ray diffraction and NMR analysis. Compounds 1–4 possessed novel cyclohexane-fused octahydroquinolizine skeletons
and represent the first quinolizidine alkaloids from the genus Myrioneuron. The epimers of cluster A (1 and 2) were modified and separated. In vitro, clusters
A and B and their derivatives inhibited replication of hepatitis C
virus (HCV, IC50 0.9 to 4.7 μM) with cytotoxicity
lower than that of telaprevir.