title: cis-Diastereoselective synthesis of chroman-fused tetralins as B-ring-modified analogues of brazilin.
abstract: We have synthesized a series ofcis-6a,7,8,12b-tetrahydro-6H-naphtho[2,1-c]chromen-6a-ols as B-ring-modified analogues of (±)-brazilin. A completely regio- andcis-diastereoselective intramolecular Friedel-Crafts epoxy-arene cyclization of 1-tetralone-derived glycidyl ethers catalyzed by Brønsted acids was used as the key step. Our worries concerning the formation ofcis-transproduct mixtures and their probable conversion to naphthopyran derivatives via dehydration of the tertiary hydroxy group were laid to rest. Additionally, the angular hydroxy group of one of the synthesized products has been reductively removed by a diastereoselective method which should be useful in future for preparing libraries of chroman-fused tetralins withtrans-stereochemistry at the ring junction.
authors.affiliation: Department of Chemical Sciences, Tezpur University, Napaam, Tezpur 784028, Assam, India.
authors.forename: Dimpee
authors.initials: D
authors.lastname: Gogoi
authors.affiliation: Department of Chemical Sciences, Tezpur University, Napaam, Tezpur 784028, Assam, India.
authors.forename: Runjun
authors.initials: R
authors.lastname: Devi
authors.affiliation: Chemical Science and Technology Division, CSIR-North East Institute of Science & Technology, Jorhat 785006, Assam, India.
authors.forename: Pallab
authors.initials: P
authors.lastname: Pahari
authors.affiliation: Department of Chemical Sciences, Tezpur University, Napaam, Tezpur 784028, Assam, India.
authors.forename: Bipul
authors.initials: B
authors.lastname: Sarma
authors.affiliation: Department of Chemical Sciences, Tezpur University, Napaam, Tezpur 784028, Assam, India.
authors.forename: Sajal Kumar
authors.initials: SK
authors.lastname: Das
keywords: brazilin; chroman; epoxy-arene cyclization; natural-product-like molecules; tetralin