科研之友
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摘要
Substrate control in target-oriented synthesis is generally important in establishing the required stereogenic center rather than reagent control. During the course of the total synthesis toward Gibberellin A(3) (1), a model compound (21) as the A-ring of 1 was accomplished in five overall steps with an overall yield of 15%, starting from furfural through conjugate addition of lithium trimethylzincate to oxabicyclo[2.2.1]heptadienedicarboxylic ester (2) as the key step. Relative to more common lithium dimethylcuprate or aluminum reagents, this zincate complex showed a complete selectivity with higher reactivity than with other simple enone compounds. The incoming methyl group was 100% selective from the ring oxygen side of 2, and the enolate intermediate can be protonated stereoselectivly without the bridge-oxygen-ring opening.
- 出版日期2012-4
- 单位清华大学
