10.1002/anie.200500466
The study presents the first total synthesis of cavicularin (1), a complex natural product derived from the liverwort Cavicularia densa, which features a strained macrocyclic core with a unique boat-like configuration of one of its arenes. The synthesis involved a radical-induced transannular ring contraction as a key step. Key chemicals used in the study include isovanillin (protected as a dioxolane acetal), 4-fluorobenzaldehyde, sodium borohydride, CBr4/PPh3, neopentyl glycol, DCC, the Herrmann catalyst, DIBALH, and various other reagents for coupling, cyclization, and protection/deprotection steps. These chemicals served to construct and modify the AD and BC ring systems, facilitate cyclization, and ultimately achieve the macrocyclic structure of cavicularin. The study also transformed the macrocyclic precursor into riccardin C, completing the shortest synthesis of this natural product to date.
10.1021/ol901136w
The research explores a method for chain elongation of 1,3-polyols through iterative enantioselective carbonyl allylation under iridium-catalyzed transfer hydrogenation conditions. The purpose is to develop a more efficient and step-economical approach to synthesizing 1,3-polyols by performing carbonyl allylation directly from the alcohol oxidation level, avoiding the use of stoichiometric organometallic reagents and unstable intermediates. Key chemicals used include allyl acetate, various alcohols such as O-benzyl 1,3-propylene glycol and neopentyl glycol, and chiral iridium catalysts modified with ligands like (R)- or (S)-Cl,MeO-BIPHEP. The study concludes that high levels of catalyst-directed enantioselectivity and diastereoselectivity can be achieved, allowing for the iterative synthesis of higher 1,3-polyols with exceptional optical enrichment. This method circumvents the need for multistep preparation of chiral allylmetal reagents and the generation of unstable α-alkoxy aldehydes, demonstrating a concise and efficient route for the synthesis of 1,3-polyols. Future work will focus on developing related C-C bond forming transfer hydrogenations, including imine additions from the amine oxidation level.
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