Michael-type quinolizidine ring

Scheme 9. Key Michael-type quinolizidine ring closure reaction of piperidine 17...

In order to introduce a carbon unit into the 2-position of the quinolizidine skeleton which would be obtained by ring cleavage of the dihydrofuran ring, we have investigated Michael type addition to the p -position of the enone moiety. When the tetrahydrofuran was treated with LDA at -78 followed by treatment of methanol, the tetrafuran ring was nicely cleaved as expected to afford the enone with 2-hydroxyethyl group at the 3-position in good yield. 

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