Condensed Emodin Derivatives and Their Applicability for the Synthesis of a Fused Heterocyclic Hypericin Derivative

Abstract

Investigations on the bifunctionalization of emodin at C(6) and C(7) with respect to the synthesis of a new class of fused heterocyclic hypericin derivatives were undertaken. The synthesis of such complex anthraquinone derivatives is possible by applying a Marschalk‐type reaction with emodin‐6‐carbaldehyde as the key step. The newly synthesized pyridazinone‐fused hypericin derivative possesses a satisfying bathochromically shifted absorption maximum making it a promising candidate for further investigations concerning a possible application in photodynamic therapy. Furthermore, the herein described strategy for the bifunctionalization of emodin provides a novel route for the synthesis of anthraquinone derivatives that are difficult to obtain by other methods.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Hypericins as Potential Leads for New Therapeutics

“…The observation that nitrogen containing heterocyclically substituted derivatives presented a pronounced bathochromically shifted absorption spectra, led to the design of a new series of derivatives, where the hypericin chromophore was fused with nitrogen containing heterocyclic rings: phthalazines, phthalazinones and pyridazinones [ 63 ]. Generally, the improved photochemical properties of these derivatives are attributed to the nature of the fused aromatic heterocycle which allows an efficient delocalization of the π-electrons of the phenanthroperylenequinone moiety.…”

Cationic Hypericin Derivatives as Novel Agents with Photobactericidal Activity: Synthesis and Photodynamic Inactivation of Propionibacterium acnes

“…To avoid a cycloaddition between the two adjacent double bonds in the corresponding hypericin derivatives, the products 3 and 4 thus available in modest yields could be easily and nearly quantitatively hydrogenated using palladium on charcoal as catalyst and methanol as solvent under ambient conditions to 5 and 6. The latter were deprotected and reduced in acceptable yields to the anthrone derivatives 7 and 8 in the common way (12)(13)(14)(15)(16)(17) using SnCl 2 ⁄ HBr in glacial acetic acid. Dimerization by means of Fe(SO 4 ) 2 ⁄ pyridine-N-oxide in pyridine and piperidine as the catalyst (12)(13)(14)(15)(16)(17) provided the protohypericin derivatives 9 and 10, which were immediately photocyclized to the hypericin derivatives 11 and 12.…”

“…During the last decade its fundamental chromophore has been derivatized in order to generate second-generation agents (11). These efforts resulted in analogs with redshifted absorption spectra to provide compounds excitable at wavelengths with enhanced penetration depth on the one hand (12)(13)(14)(15)(16)(17), and better physicochemical properties, e.g. higher solubility under physiological conditions or targeting of specific cellular sites, on the other hand (18)(19)(20)(21)(22)(23)(24)(25).…”

Rapid, Eco‐friendly, and One‐pot Synthesis of New Lariat Ethers Based on Anthraquinone by Using ZnO Nanoparticles via “Mannich” Reaction under Solvent‐free Condition

“…The anthraquinone group is a basic part of a large number of organic molecules, biological compounds, and supramolecular systems with application in several fields. For example, various 9,10‐anthraquinone derivatives have been investigated and applied as antitumor agents , antibiotics , pigments in dyestuff , and photoactive chemosensors , as well as used in synthesis of various crown ethers .…”