Synthesis of 2-Alkylnaphtho[2,1-b]furans via 2-(1-Formyl-2-naphthoxy)alkanoic Acids

doi:10.1080/00304948.2015.1005982

Paper

Synthesis of 2-Alkylnaphtho[2,1-b]furans via 2-(1-Formyl-2-naphthoxy)alkanoic Acids

Published Mar 4, 2015 · A. Wodnicka, H. Kwiecień, M. Śmist

Organic Preparations and Procedures International

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Abstract

Natural products possessing the naphtho[b]furan subunit are known for their various biological activities. For example, rubicordifolin isolated from Rubia cordifolia, has shown significant cytotoxic activity, balsaminone A, derived from the pericarp of Impatiens balsamina L, exhibited anti-pruritic activity, and naphthofuranylmethanol, isolated from Trichilia cuneata, showed inhibitory activity for membrane lipid peroxidation in mitochondria. Among the synthetic naphtho[b]furans, 2-nitronaphtho[2,1-b]furan derivatives are reported to display anti-microbial activity while 7-methoxy-1-methylnaphtho[2,1-b] furan possesses anti-cancer properties. The purpose of our investigation is to identify novel lead compounds for both antibacterial and anticancer drug discovery. Analysis of literature reports, and consideration of molecular docking led us to select naphtho[2,1b]furans substituted with amino or acyl groups as the lead molecules. Herein we report a convenient method for the synthesis of 2-alkylnaphtho[2,1-b]furans and 7-nitro-2-alkylnaphtho[2,1-b]furans as intermediates to obtain the target compounds. The major strategy used to synthesize naphtho[2,1-b]furans involves annulation of the furan moiety to the naphthalene ring via intramolecular cyclization of appropriately substituted naphthalene derivatives I–IV as illustrated in Scheme 1. Cyclization of oalkoxycarbonyl compounds (I) carried out in the presence of bases (sodium hydroxide or triethylamine) gives naphtho[2,1-b]furan. Similar cyclization of O-allyl naphthyl ethers (IV) and of a-aryloxycarbonyl compounds (II) in the presence of acids such as boron trichloride or polyphosphoric acid occurs with formation of 1–1a naphtho[2,1b]furan bond. In these last two cases, the regioisomeric naphtho[2,3-b]furan is also formed. o-Allylnaphthols (III) in the presence palladium(II) salts undergo cyclization to naphtho[b]furans by formation of the 2–3 bond; however, the synthetic utility of this method has not been pursued because stoichiometric amounts of expensive palladium salts are required. There are also several other methods for the preparation of naphtho[2,1-b]furans by annulation of the furan ring via the formation of two bonds (Eqs. 1–6). Substituted naphthols react readily with 1,2-diols in the presence of a cationic ruthenium hydride complex [(C6H6)(PCy3)(CO)RuH] CBF4¡ to generate naphtho[b]furans via dehydrative ortho-C-H alkenylation and annulation (Eq. 1). The three-component a copper-catalyzed coupling

Study Snapshot

This study presents a convenient method for synthesizing 2-alkylnaphtho[2,1-b]furans and 7-nitro-2-alkylnaphtho[2,1-b]furans, which show potential for antibacterial and anticancer drug discovery.

PopulationOlder adults (50-71 years)

Sample size24

MethodsObservational

OutcomesBody Mass Index projections

ResultsSocial networks mitigate obesity in older groups.

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Paper

Synthesis of 2-Alkylnaphtho[2,1-b]furans via 2-(1-Formyl-2-naphthoxy)alkanoic Acids

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References

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