Photo-oxidative cyclization of morusin.

13 C NMR Spectra of Chromeno-and Prenylated Flavones Structure Revision of Mulberrin, Mulberrochromene, Cyclomulberrin and Cyclomulberrochromene

“…The 13 C-NMR spectroscopy of various flavonoids and their derivatives has been extensively studied in the past few years [1][2][3][4][5][6][7]. In the course of our work [2,6,7] on the i 3 C NMR spectra of 5,7-dihydroxy flavonoids, the C-6 and C-8 resonances were always found in the interval 90.0 ppm to 100.0 ppm.…”

“…This could have differentiated between an angular and linear structures for mulberrochromene. Thus in this case 13 C NMR spectroscopy is more reliable in determining the position of C-alkylation in 5,7-dihydroxy flavones.…”

“…In the 13 C NMR spectrum of the linear chromeno-flavone (6), synthesized according to the method of Hlubucek et al [9], the C-8 signal appeared at 94.8 ppm. Similarly the chemical shift of C-4 in the 13 C NMR spectra of the linear chromeno-xanthones [10] Jacareubin, its 6-deoxy derivative, calabaxanthone, and thwaitesixanthone appeared in the narrow range 94.0 ppm to 94.8 ppm ( cyclomorusin, as compared with the parent compounds. This is typical of angular chromenoflavones [14].…”

“…In subsequent work on the same plant source Nomura et al [12,13] isolated three flavones morusin, cyclomorusin, compound A and Kuwanon C. All these compounds were given the 8-C-alkylated structures. This was on the basis of the negative Gibbs test in the case of derivatives in which only 5-OH was free.…”

ChemInform Abstract: New Constituents of Artocarpus rigida.

“…Results and Discussion. The 1 H-NMR data of 1 were very similar to those of compound A, except for the lack of signals due to a 2,2-dimethylpyran ring and the appearance of signals due to a 2-methyl-2-(4-methylpent-3-enyl)pyran ring [4] ] ). The IR absorptions of 1 implied the presence of OH (3435 cm À1 ), conjugated CO (1653 cm À1 ), and aromatic-ring (1606 cm À1 ) moieties.…”