Structure of Pummeloquinoe, a New Coumarin-Naphthoquinone Dimer Isolated form Citrus Plants

Abstract

Pummeloquinone (1), the third example of a coumarin-naphthoquinone dimer from a natural source, was isolated form the roots of several hybrid seedlings resulting from a cross of May pummelo x Marsh grapefruit (Rutaceae) grown in an orchard at Okitsu, Shizuoka, and its structure was elucidated by chamical and spectrometric methods. Synthesis of 1 was also achieved by Diels-Alder reaction between trans-dehydroosthol (3) and 2-methoxy-1, 4-benzoquinone followed by 2, 3-dichloro-5, 6-dicyano-1, 4-benzoquinone (DDQ) oxidation.