《Table 1.Hydration of 14 to 15/16.》

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《木藜芦毒素Ⅲ关键中间体的合成改进（英文）》

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With the alkylated compound 14 in hand，we investigated the hydration of vinyl group to form theγ-lactone ring using Mukaiyama’s procedure[14–16].Table 1 summarizes the results of reaction conditions for the hydration.We initially used Co（acac）2 as the catalyst and i PrOH as the solvent（entry 1），successfully obtaining the intermediate peroxide，which was reduced by PPh3 to provide 15 and 16in a 25%combined yield as a pair of C10 diastereoisomers in a ratio of 1:1.The relative configurations of 15 and 16were determined by extensive NMR spectral analysis（see Supporting Information）.The stereocenter at C10generated here will be disappeared by oxidation according to Haruhisa Shirahama group’s procedure，therefore theoretically both 15 and 16 can be transformed into the advanced intermediate[9].Encouraged by this preliminary result，we screened several catalysts and identified Mn（dpm）3 as the most promising catalyst for the hydration，which provided 15 and 16 in 72%with a ratio of 1:1.To further optimize this transformation，we next examined the solvent effects.However，when the reaction was carried out in EtOH，t Bu OH，or DCE（entries 5?7，Table 1），the yield of the desired product was dramatically decreased.Therefore，it was found that Mn（dpm）3/i PrOH was the best condition for the hydration of 14.