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(-)-α-Conidendrin 1 was synthesized according to a general reactionscheme that could be applied to other retrolignans as well. Thus, treatment of the optically active β-benzyl-γ-butyrolactone (R)-(+)-4 with NBS, followed with benzyl alcohol, selectively introduced a benzyloxy group in the benzylic position and afforded the mixture of epimers 7. α-Alkylation of the lithium enolate of the corresponding silyl ethers 10, with O-benzylvanillyl bromide 11, gave the trans disubstituted lactones 13 (2 epimers). Catalytic hydrogenolysis (Pd-C) of 13 selectively split the aryl benzyl ether linkage, and gave the compounds 14. Intramolecular Friedel-Crafts cyclization of the latter, using the benzyloxy group as the leaving group, was induced with BF3-Et2O and afforded (-)-α-conidendrin 1 in 36% overall yield from methyl α-vanillylhemis uccinate (R)-(+)-17.
- Boissin, Partrick,Dhal, Robert,Brown, Eric
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p. 687 - 694
(2007/10/02)
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- FIRST TOTAL SYNTHESIS OF (-)-α-CONIDENDRIN
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Regioselective introduction of a benzoxy group, in the benzylic position of the β-benzyl-γ-butyrolactone (R)-(+)-8, was achieved by treatment with NBS followed with benzyl alcohol. α-Alkylation of the lithium enolate of the resulting intermediate 11, with
- Boissin, Patrick,Dhal, Robert,Brown, Eric
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p. 4371 - 4374
(2007/10/02)
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