Sophopterocarpan A, a novel pterocarpine derivative with a benzotetrahydrofuran-fused bicyclo [3.3.1] nonane from Sophora flavescens

Sophopterocarpan A (1), with a novel benzotetrahydrofuran-fused bicyclo [3.3.1] nonane ring, was isolated from the roots of Sophora flavescens Ait.