Concise Synthesis of Deoxylimonin

Limonoids are a large group of plant triterpenoids that are notable for causing delayed bitterness in citrus fruits, being active in-gredients in biopesticides, and having beneficial effects on human health. Herein, we present a concise synthesis of the flagship member of limonoids, deoxylimonin, by a bioinspired skeletal reorganization approach. Key features of this synthesis include a stereoconvergent radical polyene cyclization to assemble the 6/6/6 tricyclic system, an oxime-directed Baldwin–Sanford oxida-tion to hydroxylate the unactivated C7–H, a titanium-mediated intermolecular aldol reaction to introduce the 3-furanyl lactone moiety and two contiguous stereogenic centers, and a biomimetic transesterification–oxa-Michael addition cascade to install the tetrahydrofuran-δ-lactone-fused motif. This work emphasizes the power of bioinspired skeletal reorganization in the simplified synthesis of complex terpenoids.