Multigram Synthesis of a Water-Soluble Porphyrazine and Derived seco-Porphyrazine Labeling Agents

S-seco-porphyrazine as a new member of the seco-porphyrazine family - Synthesis, characterization and photocytotoxicity against cancer cells

An important subgroup within the porphyrazine (Pz) family constitutes seco-porphyrazines, in the chemical structure of which one pyrrole unit is opened in the oxidative process. So far, there are only limited data on N-seco- and C-seco-Pzs. Here, the synthesis of a novel member of the Pzs seco-family, represented by an S-seco-tribenzoporphyrazine analogue, 22,23-bis(4-(3,5-dibutoxycarbonylphenoxy)butylsulfanyl)tribenzo[b,g,l]-22,23-dioxo-22,23-seco-porphyrazinato magnesium(II), is reported, with moderate 34% yield. The new derivative was characterized using NMR spectroscopy, UV-Vis spectroscopy, and mass spectrometry. In the photochemical study performed following the indirect chemical method with 1,3-diphenylisobenzofuran, S-seco-Pz revealed a high singlet oxygen quantum yield of 0.27 in DMF. Potential photocytotoxicity of S-seco-Pz was assessed in vitro on three cancer cell lines - two oral squamous cell carcinoma cell lines derived from the tongue (CAL 27, HSC-3) and human cervical epithelial adenocarcinoma cells (HeLa). In the biological study, the macrocycle was tested in its free form and after loading into liposomes. It is worth noting that S-seco-Pz was found to be non-toxic in the dark, with cell viability levels over 80%. The photocytotoxic IC₅₀ values for free S-seco-Pz were 0.61, 0.18, and 4.1 µM for CAL 27, HSC-3 and HeLa cells, respectively. Four different liposomal compositions were analyzed, and the cationic liposomes revealed the highest photokilling efficacy, with the IC₅₀ values for CAL 27, HSC-3, and HeLa cells at 0.24, 0.25, and 0.31 µM, respectively. The results of the photocytotoxicity study indicate that the new S-seco-tribenzoporphyrazine can be considered as a potential photosensitizer in photodynamic therapy of cancer, along with the developed cationic liposomal nanocarrier.

Microwave assisted solid-phase synthesis of substituted tetraazaporphyrins and a phthalocyanine-peptide conjugate

Various asymmetrically substituted phthalocyanines (Pcs) and porphyrazines (Pzs) have been synthesized in good yields using a solid-phase synthesis method with a poly(ethylene glycol) (PEG) resin attached to an indole linker as the solid support. These compounds are formed by cross condensation of maleonitrile or phthalonitrile with another phthalonitrile covalently bonded to the solid support with an amino linking group. The polymer bound Pc or Pz is separated by filtration, and washing the symmetrical Pc or Pz by-product. The amine Pc -appended to polyethylene glycol resin is further reacted to yield azide whilst still on the solid support. Cleavage of the Pc or Pz off the solid support results in 3:1 asymmetric Pz or Pz with high degree of purity, requiring minimal further purification. The use of hydrophilic PEG-based resin allows the symmetrical compound to be removed completely by washing whereas the acid labile indole linker makes it easier to cleave the product under mild conditions. The conjugation abilities of these compounds have been demonstrated by the successful conjugation of one of the azide Pcs with a peptide elaborated with an alkyne function. Use of microwave for the synthesis of these compounds results in shorter reaction times, higher yields and higher degree of purity.

Porphyrazines: Designer Macrocycles by Peripheral Substituent Change

It is rare that such a diverse array of applications can be realized from a single basic molecular unit, however, such is the power of the tetrapyrrolic macrocycle motif. Indeed, their potential in areas such as chemical dyes, optical sensors, optoelectronics, and biomedical agents is a function of their rich electronic and optical properties. While the naturally occurring porphyrins and the synthetic phthalocyanines have been extensively studied, the related tetraazaporphyrins or porphyrazines remain comparatively underdeveloped. Since porphyrazines maintain a unique position in this family: analogous derivatives are virtually inaccessible for the porphyrins, and direct fusion of heteroatomic substituents onto the porphyrazine β-positions results in a more pronounced effect compared with the substitution of an equivalent group onto the benzenoid rings of the phthalocyanine; a driving force exists to further explore the synthesis and applications of these novel macrocycles. This review will provide a historical overview of the synthetic strategies towards functionalized porphyrazines and describe new strategies towards the preparation and applications of heteroatom-appended porphyrazines, particularly in the context of their multimetallic complexes, catalysis, surface chemistry, and as biomedical agents.