Synthesis of diverse catechin congeners via diastereoselective intramolecular epoxy-arene cyclization

Add time:08/06/2019    Source:sciencedirect.com

While there have been large amount of research activities on the chemistry and biology of catechins (flavan-3-ols/2-arylchroman-3-ols) and their derivatives, the systematic synthetic and bioevaluation studies of congeneric 4-arylchroman-3-ols remain a less explored area. Towards that objective, we have synthesized twenty eight 4-arylchroman-3-ols with different substitution patterns on both the aromatic rings in high stereo- and regioselectivity via intramolecular epoxy-arene cyclization of 2-(aryloxymethyl)-3-aryloxiranes. The defined protocol is metal-free using 20 mol % of p-toluene sulfonic acid monohydrate (TsOH.H2O) as Brønsted acid catalyst. Depending on the electronic nature of the attacking aromatic ring during the epoxide ring-opening, the products are formed in moderate to high yields. Additionally, this method has the advantage that it neither needs strict anhydrous conditions nor suffers from the use of expensive Lewis/Brønsted acids. We have also developed an efficient method to convert trans-4-arylchroman-3-ols to their corresponding cis-isomers and demonstrated its application by synthesizing a chroman-fused 2,3-dihydrobenzofuran derivative.

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