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Download fileTotal Syntheses of (+)-Alopecuridine, (+)-Sieboldine A, and (−)-Lycojapodine A
journal contribution
posted on 2012-09-21, 00:00 authored by Xiao-Ming Zhang, Hui Shao, Yong-Qiang Tu, Fu-Min Zhang, Shao-Hua Wang(+)-Alopecuridine, (+)-sieboldine A, and (−)-lycojapodine
A, three structurally unique and related lycopodium alkaloids, have
been synthesized in enantiomeric forms through an efficient strategy.
The main synthetic approach for (+)-alopecuridine features a semipinacol
rearrangement of hydroxyl epoxide to construct the spiro 6,9-azacarbocycles
with an all-carbon quaternary center and a late-stage SmI2-mediated intramolecular coupling to form the 5-membered ring. Subsequently,
the biomimetic synthesis of (+)-sieboldine A and (−)-lycojapodine
A was accomplished successfully through two different bioinspired
oxidations after a wide search for the oxidation methods. As a result,
(+)-sieboldine A was derived from (+)-alopecuridine through an N-oxidation/nitrone
formation process and (−)-lycojapodine A through an interesting
cyclic hemiketal formation/oxidative diol cleavage pathway. These
results confirmed the biogenetic relationship among the three alkaloids.