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

Six unusual matrine-type alkaloid dimers, flavesines A–F (<b>1–6</b>, respectively), together with three proposed biosynthetic intermediates (<b>7–9</b>) were isolated from the roots of <i>Sophora flavescens</i>. Compounds <b>1–5</b> were the first natural matrine-type alkaloid dimers, and compound <b>6</b> 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 <b>1–6</b> were also proposed. Compounds <b>1–9</b> exhibited inhibitory activities against hepatitis B virus