A concise total synthesis of biologically active frutinones via tributylphosphine-catalyzed tandem acyl transfer-cyclization
摘要:
A concise and step-economical total synthesis of biologically active frutinones has been achieved. Tributylphosphine (PBu3) efficiently induced the tandem acyl transfer-cyclization of carbonates 5 to afford 3-methoxycarbonylflavone derivatives 4 in excellent yields. Finally, concomitant deprotection and lactonization under acidic conditions furnished the desired frutinones A (1a), B (1b), and the proposed structure of frutinone C (1c). (C) 2014 Elsevier Ltd. All rights reserved.
Alcohol Mediated Synthesis of 4-Oxo-2-aryl-4<i>H</i>-chromene-3-carboxylate Derivatives from 4-Hydroxycoumarins
作者:Manoj R. Zanwar、Mustafa J. Raihan、Sachin D. Gawande、Veerababurao Kavala、Donala Janreddy、Chun-Wei Kuo、Ram Ambre、Ching-Fa Yao
DOI:10.1021/jo301044y
日期:2012.8.3
The unusual alcohol mediated formation of 4-oxo-2-aryl-4H-chromene-3-carboxylate (flavone-3-carboxylate) derivatives from 4-hydroxycoumarins and β-nitroalkenes in an alcoholic medium is described. The transformation occurs via the in situ formation of a Michael adduct, followed by the alkoxide ion mediated rearrangement of the intermediate. The effect of the different alcohol and nonalcohol media on
Asymmetric Transfer Hydrogenation of 2,3-Disubstituted Flavanones through Dynamic Kinetic Resolution Enabled by Retro-Oxa-Michael Addition: Construction of Three Contiguous Stereogenic Centers
A ruthenium-catalyzed asymmetric transfer hydrogenation of 2,3-disubstituted flavanones was developed for the construction of three contiguous stereocenters under basic conditions through a combination of dynamic kinetic resolution and retro-oxa-Michael addition, giving chiral flavanols with excellent enantioselectivities and diastereoselectivities. The reaction proceeded via a base-catalyzed retro-oxa-Michael