Formation of 3,4‐Diarylpyrrole‐ and Pyrrolocoumarin Core of Natural Marine Products via Barton–Zard Reaction and Selective O‐Demethylation
Eugenia A. Silyanova, A. V. Samet, Lev K. Salamandra, Victor N. Khrustalev, Victor V. Semenov
Abstract
A metal‐free approach to 3,4‐diarylpyrrole‐2‐carboxylate and pyrrolocoumarin cores of lamellarins and related natural products based on Barton–Zard reaction of nitrostilbenes with ethyl isocyanoacetate was developed. In the case of diarylpyrrole‐2‐carboxylates with a 3‐( o ‐methoxyphenyl) fragment, treatment with 1 equiv. of. BBr 3 resulted in selective O‐demethylation of the ortho ‐methoxy group, while other methoxy groups in the molecule remained intact. The resulting 3‐(2‐hydroxyphenyl)pyrrole‐2‐carboxylates underwent base‐induced lactonization to form the target pyrrolocoumarins.
Topics & Concepts
ChemistryDemethylationPyrroleCarboxylateStereochemistryFree baseMoleculeOrganic chemistryMedicinal chemistrySalt (chemistry)Gene expressionBiochemistryDNA methylationGeneSynthesis and Characterization of PyrrolesOxidative Organic Chemistry ReactionsAsymmetric Synthesis and Catalysis