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Concise Syntheses of bis‐Strychnos Alkaloids (−)‐Sungucine, (−)‐Isosungucine,and (−)‐Strychnogucine B from (−)‐Strychnine |
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| Authors: | Dr Senzhi Zhao Christiana N Teijaro Heng Chen Dr Gopal Sirasani Dr Shivaiah Vaddypally Prof?Dr Michael J Zdilla Prof?Dr Graham E Dobereiner Prof?Dr Rodrigo B Andrade |
| Institution: | Department of Chemistry, Temple University, St. Philadelphia, Pa, USA |
| Abstract: | The first chemical syntheses of complex, bis‐Strychnos alkaloids (?)‐sungucine ( 1 ), (?)‐isosungucine ( 2 ), and (?)‐strychnogucine B ( 3 ) from (?)‐strychnine ( 4 ) is reported. Key steps included (1) the Polonovski–Potier activation of strychnine N‐oxide; (2) a biomimetic Mannich coupling to forge the signature C23?C5′ bond that joins two monoterpene indole monomers; and (3) a sequential HBr/NaBH3CN‐mediated reduction to fashion the ethylidene moieties in 1 – 3 . DFT calculations were employed to rationalize the regiochemical course of reactions involving strychnine congeners. |
| Keywords: | alkaloids biomimetic synthesis natural products strychnine sungucine |