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A Remarkable Photoreaction of 3‐ O ‐Benzylhypericin
Author(s) -
Dax Thomas G.,
Kapinus Evgeny I.,
Falk Heinz
Publication year - 2000
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/1522-2675(20000809)83:8<1744::aid-hlca1744>3.0.co;2-c
Subject(s) - chemistry , hypericin , benzene , acetone , aqueous solution , irradiation , photochemistry , proton , acetal , stereochemistry , medicinal chemistry , organic chemistry , medicine , physics , quantum mechanics , nuclear physics , pharmacology
Irradiation of 3‐ O ‐benzylhypericin dissolved together with at least 1 equiv. of `proton sponge' in benzene was shown, by means of UV/VIS, 1 H‐NMR, and mass spectrometric measurements, to produce the rearranged blepharismin‐analogous 11‐phenyl‐11 H ‐benz[4,10]anthra[2,1,9,8‐ nopqa ]pleiadene system. The latter compound yielded hypericin when treated with light and oxygen in acetone solution, followed by aqueous NH 4 Cl. This reaction is considered to proceed via the oxybleopharismin‐analog 3,4‐benzal acetal of hypericin. The implications of the novel phototransformation for synthesis and biosynthesis of the natural products, as well as the structural peculiarities of the photoproducts, are discussed.