- Biomimetic oxidative transformations of pericine: partial synthesis of apparicine and valparicine, a new pentacyclic indole alkaloid from Kopsia
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A new pentacyclic indole alkaloid of the pericine-type, valparicine, representing the first member of this sub-group, was obtained from a Malayan Kopsia species and the structure was established by spectroscopic analysis. A partial synthesis of valparicine and apparicine from pericine was carried out via the Potier-Polonovski reaction and the biogenetic implications are discussed.
- Lim, Kuan-Hon,Low, Yun-Yee,Kam, Toh-Seok
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- Total Synthesis of (±)/(+)-Subincanadine e and Determination of Absolute Configuration
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A facile synthesis of (±)-subincanadine E was described from tryptamine-based maleimide. 1,2-Addition of Grignard reagent to maleimide, internal activation of formed lactamol for in situ 1,4-addition of Grignard reagent, and associated position-specific allylic rearrangement in diastereoselective Pictet-Spengler cyclization were the key steps. Enantioselective first total synthesis of naturally occurring cytotoxic (+)-subincanadine E was also accomplished from (S)-acetoxysuccinimide via an unusual syn-addition of cuprate to the α,β-unsaturated lactam. Sinister absolute configuration was assigned to (+)-subincanadine E on the basis of total synthesis. (S)-Acetoxy group in the succinimide precursor was initially employed to impart regio- and stereoselectivity and then as a suitable leaving group to generate the desired conjugated lactam.
- Kalshetti, Manojkumar G.,Argade, Narshinha P.
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