Alstoscholactine and Alstolaxepine, Monoterpenoid Indole Alkaloids with γ-Lactone-Bridged Cycloheptane and Oxepane Moieties from Alstonia scholaris

Krishnan P , Lee FK , Chong KW 1 , Mai CW , Muhamad A 2 , Lim SH 1 Show all authors , Low YY 1 , Ting KN , Lim KH

Affiliations 

  • 1 Department of Chemistry, Faculty of Science , University of Malaya , 50603 Kuala Lumpur , Malaysia
  • 2 Malaysia Genome Institute , Jalan Bangi, 43000 Kajang , Selangor , Malaysia
Org. Lett., 2018 12 21;20(24):8014-8018.
PMID: 30543301 DOI: 10.1021/acs.orglett.8b03592

Abstract

Two new monoterpenoid indole alkaloids, alstoscholactine (1) and alstolaxepine (2), were isolated from Alstonia scholaris. Compound 1 represents a rearranged stemmadenine alkaloid with an unprecedented C-6-C-19 connectivity, whereas compound 2 represents a 6,7- seco-angustilobine B-type alkaloid incorporating a rare γ-lactone-bridged oxepane ring system. Their structures and absolute configurations were determined by spectroscopic analyses. Compound 1 was successfully semisynthesized from 19 E-vallesamine. Compound 2 induced marked vasorelaxation in rat isolated aortic rings precontracted with phenylephrine.

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