ChemInform Abstract: Synthesis of Iridolactones via Stereoselective Favorskii Rearrangement: (+)‐Dolicholactone, (+)‐Alyxialactone, and (‐)‐4‐epi‐Alyxialactone.

Abstract

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Application of Cp2TiCl-Promoted Radical Cyclization: A Unified Strategy for the Syntheses of Iridoid Monoterpenes

“…Interestingly, in spite of their confined molecular framework, they hold contiguous stereogenic centers and are characterized by a cyclopentane ring cis -fused to a dihydropyran or δ-lactone . Many approaches have been published over the years − to obtain this privileged scaffold owing to their therapeutic potential as drug candidates, and thus the furtherance in the synthesis of iridoids (Figure ) is still desired. To mention a few notable works, Hofferberth et al accessed various iridoid monoterpenes in a divergent manner from a common citronellol-derived aminal intermediate obtained by an enamine/enal cycloaddition reaction. , Mulzer et al described the free radical cyclization pathway of acyclic chirally C-2-substituted 1-hexenyl radicals to construct an iridoid carbon framework .…”

Gram-Scale Synthesis of Loganetin from S-(+)-Carvone

“…The arrangement of the four asymmetric centers on the cyclopentane ring is in agreement with loganetin. Although the Favorskii rearrangement product from S -(+)-carvone has been successfully used for the total synthesis of iridoid lactones , and other natural products, exploiting it in the total synthesis of loganetin remains unexplored. Because loganetin contains an unstable and optically active dihydropyran ring, the assembly of such a ring is more difficult than that of iridoid lactones. , The desirable synthetic strategy is to avoid the decomposition of the hemiacetal moiety and the epimerization of the stereocenter at C1.…”