Self-Assembly of 4,4'-Linked Dipyrromethanes from Unconventional Reactants─Propargylamines, 2-(Vinyloxy)ethyl Isothiocyanate, and Alkylating Agents under Basic Conditions

Self-assembly of 4,4'-linked dipyrromethanes from 2-(vinyloxy)ethyl isothiocyanate, tertiary propargylamines, and alkylating agents has been discovered. The plausible reaction mechanism, the major stages of which have been confirmed experimentally, includes (1) the lithiation of propargylamine (with n-BuLi); (2) the formation of lithium N-[2-(vinyloxy)ethyl]but-2-ynimidothioate (product of the addition of monolithiated propargylamine to isothiocyanate); (3) isomerization of the latter in the corresponding allenylimidothioate (under the action of the t-BuOK/t-BuOH system); (4) low-temperature (<15 °C) intramolecular cyclization of the latter into potassium N-(5-amino-2-thienyl)-N-[2-(vinyloxy)ethyl]amide; (5) the base-induced cleavage of the C-O bond of the N-[2-(vinyloxy)ethyl] group and removal of vinyloxide-anion leading to acetaldehyde; (6) interaction of acetaldehyde with two molecules of N-(5-amino-2-thienyl)-N-[2-(vinyloxy)ethyl]amide-anion resulting in dithienomethane N-anionic intermediate; (7) recyclization of the latter into dipyrromethane S-anionic intermediate. Final S-alkylation affords synthetically challenging 4,4'-dipyrromethanes in a yield of 22-51%. The whole process is carried out in a single synthetic operation in a very short time (∼10-15 min, excluding alkylation time).

Evaluation of singlet oxygen generators of novel water-soluble perylene diimide photosensitizers

In this study, novel photosensitizers using three water-soluble green perylene diimide (PDI)-based ligands were synthesized, which can be used as photosensitizing drugs in photodynamic cancer therapy (PDT). These three efficient singlet oxygen generators were prepared via reactions of three newly designed molecules, namely 1,7-di-3-morpholine propylamine-N,N'-(l-valine-t-butylester)-3,4:9,10-perylyne diimide, 1,7-dimorpholine-N,N'-(O-t-butyl-l-serine-t-butylester)-3,4:9,10-perylene diimide and 1,7-dimorpholine-N,N'-(l-alanine t-butylester)-3,4:9,10-perylene diimide. Although there have been numerous photosensitizers, most of them have a limited useable range of solvent conditions or low photostability. These sensitizers have demonstrated strong absorption and red-light excitation. The singlet oxygen production of the newly synthesized compounds was investigated using a chemical method with 1,3-diphenyl-iso-benzofuran as a trap molecule. In addition, they do not have any dark toxicity at the active concentrations. Owing to these remarkable properties, we demonstrate the singlet oxygen generation of these novel water-soluble green perylene diimide (PDI) photosensitizers with substituent groups at the 1 and 7 positions of the PDI material, which are promising for PDT.

Two birds one stone: β-fluoropyrrolyl-cysteine SNAr chemistry enabling functional porphyrin bioconjugation

Bioconjugation, a synthetic tool that endows small molecules with biocompatibility and target specificity through covalent attachment of a biomolecule, holds promise for next-generation diagnosis or therapy. Besides the establishment of chemical bonding, such chemical modification concurrently allows alteration of the physicochemical properties of small molecules, but this has been paid less attention in designing novel bioconjugates. Here, we report a "two birds one stone" methodology for irreversible porphyrin bioconjugation based on β-fluoropyrrolyl-cysteine S_NAr chemistry, in which the β-fluorine of porphyrin is selectively replaced by a cysteine in either peptides or proteins to generate novel β-peptidyl/proteic porphyrins. Notably, due to the distinct electronic nature between fluorine and sulfur, such replacement makes the Q band red-shift to the near-infrared region (NIR, >700 nm). This facilitates intersystem crossing (ISC) to enhance the triplet population and thus singlet oxygen production. This new methodology features water tolerance, a fast reaction time (15 min), good chemo-selectivity, and broad substrate scope, including various peptides and proteins under mild conditions. To demonstrate its potential, we applied porphyrin β-bioconjugates in several scenarios, including (1) cytosolic delivery of functional proteins, (2) metabolic glycan labeling, (3) caspase-3 detection, and (4) tumor-targeting phototheranostics.

Lanthanide porphyrinoids as molecular theranostics

In recent years, lanthanide (Ln) porphyrinoids have received increasing attention as theranostics. Broadly speaking, the term 'theranostics' refers to agents designed to allow both disease diagnosis and therapeutic intervention. This Review summarises the history and the 'state-of-the-art' development of Ln porphyrinoids as theranostic agents. The emphasis is on the progress made within the past decade. Applications of Ln porphyrinoids in near-infrared (NIR, 650-1700 nm) fluorescence imaging (FL), magnetic resonance imaging (MRI), radiotherapy, and chemotherapy will be discussed. The use of Ln porphyrinoids as photo-activated agents ('phototheranostics') will also be highlighted in the context of three promising strategies for regulation of porphyrinic triplet energy dissipation pathways, namely: regioisomeric effects, metal regulation, and the use of expanded porphyrinoids. The goal of this Review is to showcase some of the ongoing efforts being made to optimise Ln porphyrinoids as theranostics and as phototheranostics, in order to provide a platform for understanding likely future developments in the area, including those associated with structure-based innovations, functional improvements, and emerging biological activation strategies.

Combination of tetrapyridylporphyrins and arene ruthenium(II) complexes to treat synovial sarcoma by photodynamic therapy

Four tetrapyridylporphyrin and four dipyridylporphyrin arene ruthenium complexes have been synthesized and characterized. In these complexes, the porphyrin core is either metal-free or occupied by zinc, and the arene ligand of the arene ruthenium units are either the standard methyl-isopropyl-benzene ([Formula: see text]cymene) or the less common phenylpropanol (PhPrOH) derivative. The porphyrin derivatives are coordinated to four arene ruthenium units or only two, in accordance with the number of pyridyl substituents at the periphery of the porphyrins, 5,10,15,20-tetra(4-pyridyl)-21H,23H-porphine (TPyP) and 5,15-diphenyl-10,20-di(pyridin-4-yl)porphyrin (DPhDPyP). All eight complexes were evaluated as anticancer agents on synovial sarcoma cells, in the presence and absence of light, suggesting that both the arene ligand and the porphyrin core substituent can play a crucial role in fine-tuning the photodynamic activity of such organometallic photosensitizers.