Synthesis of Naturally Occurring Pyranonaphthoquinones: (±) 9-Demethoxyeleutherin, (±) 9-Demethoxyisoeleutherin, and Pentalongin via Nef Reaction

Abstract

The article describes alternative method for the synthesis of (±) 9-demethoxyeleutherin and (±) 9-demethoxyisoeleutherin, the analogs of naturally occurring pyranonaphthoquinones antibiotics eleutherin and isoeleutherin. This methodology has provided the target molecules using a shorter route involving five simple chemical transformations with Nef reaction as a key step. All the intermediates and target molecules were completely characterized by spectral techniques and confirmed by comparison with literature data. Further we have extended Nef protocol toward formal synthesis of naturally occuring pyranonaphthoquinone pentalongin. We accomplished synthesis of of 2-(1,4-dimethoxynaphthalen-2-yl)acetic acid devoid of very toxic cyanide intermediates, which has been converted into pentalongin.

GRAPHICAL ABSTRACT

Keywords:

• Eleutherin
• isoeleutherin
• Nef reaction
• pyranonaphthoquinones

ACKNOWLEDGMENTS

Authors are grateful to S. G. Gupta, principal, Abasaheb Garware College, for providing the necessary facilities and the University of Pune and Agharkar Research Institute, Pune, for providing spectral analysis.

Notes

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