Dimeric Matrine-Type Alkaloids from the Roots of Sophora flavescens and Their Anti-Hepatitis B Virus Activities

Six unusual matrine-type alkaloid dimers, flavesines A–F (1–6, respectively), together with three proposed biosynthetic intermediates (7–9) were isolated from the roots of Sophora flavescens. Compounds 1–5 were the first natural matrine-type alkaloid dimers, and compound 6 represented an unprecedented dimerization pattern constructed by matrine and (−)-cytisine. Their structures were elucidated by NMR, MS, single-crystal X-ray diffraction, and a chemical method. The hypothetical biogenetic pathways of 1–6 were also proposed. Compounds 1–9 exhibited inhibitory activities against hepatitis B virus.