cis-Diastereoselective synthesis of chroman-fused tetralins as B-ring-modified analogues of brazilin

• Dimpee Gogoi,
• Runjun Devi,
• Pallab Pahari,
• Bipul Sarma and
• Sajal Kumar Das

Beilstein J. Org. Chem. 2016, 12, 2816–2822, doi:10.3762/bjoc.12.280

• Abstract We have synthesized a series of cis-6a,7,8,12b-tetrahydro-6H-naphtho[2,1-c]chromen-6a-ols as B-ring-modified analogues of (±)-brazilin. A completely regio- and cis-diastereoselective intramolecular Friedel–Crafts epoxy–arene cyclization of 1-tetralone-derived glycidyl ethers catalyzed by Brønsted

• been reductively removed by a diastereoselective method which should be useful in future for preparing libraries of chroman-fused tetralins with trans-stereochemistry at the ring junction. Keywords: brazilin; chroman; epoxy-arene cyclization; natural-product-like molecules; tetralin; Findings The

• chroman unit occurs widely as a privileged framework in a large number of natural products (NPs), natural product-like molecules (NPLMs) and pharmaceuticals, possessing diverse biological activities [1]. (+)-Brazilin (1) and (−)-haematoxylin (2) are two structurally-related tetracyclic homoisoflavonoid

Tricyclic flavonoids with 1,3-dithiolium substructure

• Lucian G. Bahrin,
• Peter G. Jones and
• Henning Hopf

Beilstein J. Org. Chem. 2012, 8, 1999–2003, doi:10.3762/bjoc.8.226

• effective in the treatment of various conditions, such as diarrhea, dysentery, dyspepsia, leucorrhea, and diabetic complications [9][10]. The main components of H. campechianum and C. sappan are hematoxylin (3, Figure 1) and brazilin; the basic structures of the two contain a 3,4-cycloalkyl-fused benzopyran