Design and studies of novel polyoxysterol-based porphyrin conjugates

Fused Pyrroles in Cholestane and Norcholestane Side Chains: Acaricidal and Plant Growth-Promoting Effects

Herein, we describe the synthesis and characterization of fused pyrroles in cholestane and norcholestane side chains derived from kryptogenin and diosgenin, respectively. Both conventional and microwave heating techniques were used to synthesize the steroidal pyrroles from primary amines, with the microwave method producing the highest yields. In particular, the norcholestane pyrroles were tested as acaricides against the two-spotted spider mite (Tetranychus urticae Koch) under laboratory conditions and as plant growth promoters on habanero pepper (Capsicum chinense Jacq) under greenhouse conditions.

The Self-Aggregation of Porphyrins with Multiple Chiral Centers in Organic/Aqueous Media: The Case of Sugar- and Steroid-Porphyrin Conjugates

An overview of the solvent-driven aggregation of a series of chiral porphyrin derivatives studied by optical methods (UV/Vis, fluorescence, CD and RLS spectroscopies) is herein reported. The investigated porphyrins are characterized by the presence in the meso-positions of glycol-, steroidal- and glucosteroidal moieties, conferring amphiphilicity and solubility in aqueous media to the primarily hydrophobic porphyrin platform. Aggregation of the macrocycles is driven by a change in bulk solvent composition, forming architectures with supramolecular chirality, steered by the stereogenic centers on the porphyrin peripheral positions. The aggregation behavior and chiroptical properties of the final aggregated species strongly depend on the number and stereogenicity of the ancillary groups that dictate the mutual spatial arrangement of the porphyrin chromophores and their further organization in larger structures, usually detectable by different microscopies, such as AFM and SEM. Kinetic studies are fundamental to understand the aggregation mechanism, which is frequently found to be dependent on the substrate concentration. Additionally, Molecular Mechanics calculations can give insights into the intimate nature of the driving forces governing the self-assembly process. The critical use of these combined methods can shed light on the overall self-assembly process of chirally-functionalized macrocycles, with important implications on the development of chiral porphyrin-based materials.

Conjugates of 17-substituted testosterone and epitestosterone with pyropheophorbide a differing in the length of linkers

Conjugates of 17α-substituted testosterone (1 and 2) and 17β-substituted epitestosterone (3 and 4) with pyropheophorbide a were synthesized. The scheme consisted of synthesis of 17α-hydroxy-3-oxopregn-4-en-21-oic and 17β-hydroxy-3-oxopregn-4-en-21-oic acids, and their coupling with pyropheophorbide a by means of either ethylene diamine, or 1,5-diamino pentane linkers. Mutual influence of steroidal and macrocyclic fragments in conjugates molecules was dependent on configuration of C17 and length of linker, that was established by analysis of ¹H NMR spectra and molecular models of conjugates. Studies of interaction of conjugates with prostate carcinoma cells revealed that their uptake and internalization were independent on the androgen receptor activity, but dependent on the structure of conjugates, decreasing in the following row: 3 > 4 ≥ 1 > 2. Conjugates significantly decreased the LNCaP and PC-3 cells growth at 96 h incubation. Epitestosterone derivatives 3 and 4 also showed superior anti-proliferative activity versus testosterone ones. Conformationally more rigid conjugates 1 and 3, comprising short linkers, were more active than those with long linkers; conjugate 3 was the most potent.

Steroid-photosensitizer conjugates: Syntheses and applications

This review focuses on progress in the development of different approaches to the design of steroid ([Formula: see text] estrogens, androgens, cholesterol) conjugates with coordination assemblies of metalloporphyrins, phthalocyanines and related complexes. Porphyrins and phthalocyanines have received considerable attention due to their novel composition, intriguing spectroscopic, photophysical, and redox properties, and potential application in light-harvesting and optoelectronic devices. With the development of more efficient imaging and therapeutic applications, these bio-conjugates are evaluated as multimodality agents (PET, fluorescence imaging) to monitor the mechanism of action of biologically active components in living systems and as agents for molecular recognition, oxygen atom transfer and catalysis. The tetrapyrrole components, which can be coupled via covalent and various non-covalent linkages, may exhibit strong interactions through efficient photo-induced electron and/or energy transfer processes.

Comprehensive physiology and toxicology of ecdysogens--The metabolically activated porphyrin-ecdysteroid complexes in insects

The polyhydroxylated derivatives of 6-keto,7-dehydrocholesterol (ecdysone, ecdysteroids, Ecd) are natural compounds widely distributed in plants. They exhibit strong anabolic, vitamin D-like, pharmacological effects in vertebrate animals and in the human body. In the larval stages of insects, injections of pure Ecd cause serious pathophysiological, "hyperecdysonic" syndromes associated with neuromuscular paralysis, premature cuticular apolysis and complete inhibition of ecdysis. Ecds do not penetrate insect cuticle. For this reason, all previous attempts to induce ecdysone responses by topical applications of Ecd failed. In this work, we tried to induce the topical effects of Ecd by preparation of more lipophilic complexes, with 2 or 4 molecules of 20-hydroxyecdysone (E20) attached to a relatively large nucleus of the porphyrin. The resulting porphyrin-E20 complexes (ecdysogens) have been subjected to standardised assays for ecdysone activity in the ligatured larvae ("dauerlarvae") of the greater waxmoth (Galleria mellonella). Similarly like the free E20 alone, porphyrin-E20 complexes had no effect when applied on the body surface or administered in the larval diet. When injected, however, they exhibited delayed effects, but the adverse ("hyperecdysonic") pathophysiological syndromes were reduced or abolished. It is concluded, therefore, that the replacement of pathophysiological, precocious or "hyperecdysonic" moults by the larval-pupal transformation, was due to successive metabolic liberation of the biologically active, free E20 from the porphyrin-E20 complex. The biological status of Ecd does not agree with their definition as the prothoracic gland (PG) hormone of insects, nor with the assumptions about a growth hormone of plants. A possibility that the most important status of Ecd may depend on the pharmacological properties of a sterolic D6 vitamin has been discussed.

Tuning the chiroptical and morphological properties of steroidal-porphyrin aggregates: a mechanistic, structural, and MM investigation

The aggregation of a steroid-functionalised porphyrin derivative occurs with the formation of J-type chiral species. Spectroscopic and SEM studies indicate that the initial concentration of the macrocycle strongly influences the morphology of the final mesoscopic structures, as a consequence of a change in the mechanistic course of the self-assembly process. Fibrillar structures are obtained at low porphyrin concentration, whereas aggregates of globular shapes are formed on increasing the substrate concentration. Molecular mechanics investigations gave insights into the intimate nature of the driving forces that govern the self-assembly process, pointing out the importance of ring distortion, of intramolecular steroidal OH-π hydrogen bonds, as well as dispersion forces among the tetrapyrrolic platforms.

Synthesis of porphyrin-bis(polyazamacrocycle) triads via Suzuki coupling reaction

Suzuki–Miyaura cross-coupling reaction has been used for the synthesis of tricyclic architectures based on trans-A2B2-porphyrins and bisaminal-protected polyazamacrocycles which are linked directly or by a p-phenylene spacer. This modular approach allowed the synthesis of ligands with various substituted porphyrin macrocycles and bisaminal-protected tetraazamacrocycles possessing different cavity sizes. These molecules can be assembled into dimers using a DABCO linker. Deprotection of these compounds afforded porphyrin-bis(polyazamacrocycle) triads.

Synthesis of Steroid–Porphyrin Conjugates from Oestradiol, Oestrone, and Lithocholic Acid

The synthesis of porphyrin–steroid conjugates is examined using the natural steroids oestradiol, oestrone, and lithocholic acid as precursors. Two strategies differing in the timing of formation of the steroid–porphyrin linkage leading to four different construction motifs are explored. Two approaches are based on a strategy of introduction of steroidal components in the porphyrin-forming reaction involving condensation of steroidal-alkylaldehydes and pyrrole to give 5,10,15,20-tetrakis(steroidal-alkyl)porphyrins and differ in the way in which the required aldehyde is introduced to the steroidal component. In the other strategy, a steroidal component is introduced by post-porphyrin synthesis reactions and here also two approaches were explored, one involving nucleophilic substitution and the other esterification. Of the four approaches investigated, the most efficient and most versatile one attaches the steroidal components late in the sequence to a 5,10,15,20-tetra(ω-haloalkyl)porphyrin by a nucleophilic substitution reaction. In this way, a 5,10,15,20-tetrakis[oestrone-linked-heptyl)porphyrin was obtained in 47 % yield.

Surfactant-induced chirality on reluctant aggregates of a chiral amphiphilic cationic (l)-proline–Zn(ii)porphyrin conjugate in water

The aggregation of an amphiphilic chiral Zn(ii)porphyrin derivative occurs in aqueous solutions of chiral surfactants with highly specific molecular recognition.