By use of a simple synthetic methodology for peptide coupling by HATU reagent, two BODIPY amides 4 and 5 were synthesized, that were at the meso-position substituted with a morphline moiety targeting lysosomes, or sulfonamide group targeting endoplasmic reticulum (ER), respectively. Furthermore, by use of Cu-catalyzed click chemistry, dye 6 was synthesized from a BODIPY alkyne, that was at the meso-position substituted with a triphenylphosponium salt via a triazol linker, for targeting mitochondria. Photophysical and spectral properties of BODIPY dyes 4-6 were characterized in nonpolar, polar aprotic and protic solvent. All compounds in all solvents have high values of fluorescence quantum yields (Phi F = 0.5-0.8), and single-exponential decay of fluorescence with singlet excited state lifetimes tau = 2.5-3.8 ns. The substituents in the meso-position that direct the dyes towards different intracellular organelles do not affect the photophysical properties. The dyes showed excellent photostability upon irradiation in aqueous solution with 488 nm laser. Moreover, the stability of amides 4 and 5 was tested with lipases CAL-B and PPL, whereupon they showed hydrolytic stability. The applicability of dyes 4-6 in fluorescent staining of organelles in HeLa cell line was tested in colocalization microscopy studies with commercial dyes Lysotracker RED, ER tracer and Mitotracker Red. They showed excellent localization in lysosomes, ER and mitochondria with the values of Pearson's coefficients 0.90, 0.94, and 0.93, respectively. Furthermore, ability of dyes 4-6 to stain live HeLa cells was demonstrated. Consequently, BODIPY derivatives 4-6 have potential to be used in biology as selective organelle targeting dyes. Moreover, our simple synthetic protocol for the preparation of dyes in principle allows for the synthesis of plethora of different BODIPY derivatives with selective localization in different organelles.

Dipeptides 1 and 2 were synthesized from unnatural amino acids containing pyrene as a fluorescent label and polynucleotide binding unit, and modified tyrosine as a photochemically reactive unit. Photophysical properties of the peptides were investigated by steady-state and time-resolved fluorescence. Both peptides are fluorescent (Φf = 0.3–0.4) and do not show a tendency to form pyrene excimers in the concentration range < 10−5 M, which is important for their application in the fluorescent labeling of polynucleotides. Furthermore, both peptides are photochemically reactive and undergo deamination delivering quinone methides (QMs) (ΦR = 0.01–0.02), as indicated from the preparative photomethanolysis study of the corresponding N-Boc protected derivatives 7 and 8. Both peptides form stable complexes with polynucleotides (log Ka > 6) by noncovalent interactions and similar affinities, binding to minor grooves, preferably to the AT reach regions. Peptide 2 with a longer spacer between the fluorophore and the photo-activable unit undergoes a more efficient deamination reaction, based on the comparison with the N-Boc protected derivatives. Upon light excitation of the complex 2·oligoAT10, the photo-generation of QM initiates the alkylation, which results in the fluorescent labeling of the oligonucleotide. This study demonstrated, as a proof of principle, that small molecules can combine dual forms of fluorescent labeling of polynucleotides, whereby initial addition of the dye rapidly forms a reversible high-affinity noncovalent complex with ds-DNA/RNA, which can be, upon irradiation by light, converted to the irreversible (covalent) form. Such a dual labeling ability of a dye could have many applications in biomedicinal sciences.

Two BODIPY phenolic esters 1 and 2 were synthesized and their acid-catalyzed hydrolytic and esterase enzymatic stability was demonstrated. Their photophysical properties were investigated in solvents of different po-larity. Their spectral properties are the typical of BODIPY dyes with narrow absorption and emission spectra in the visible spectral region and large molar absorption coefficients (approximate to 500 nm, epsilon = 40000-50000 M-1cm- 1). The derivative with methyl substituted BODIPY core 2 shows quantum yields of fluorescence one magnitude higher (phi f = 0.30-0.55) compared to the BODIPY without methyl groups. Solvents affect very weakly spectral prop-erties, with more pronounced effect of the solvent polarizability than the solvent polarity. Both BODIPY dyes show pH responsive fluorescence in aqueous solution (pKa = 2.72 +/- 0.08 and 4.18 +/- 0.05), with quenching of fluorescence by protonation due to PET from the BODIPY to phenol, rendering them applicable for intracellular pH measurements. The feasibility of the PET in the protonated form of 1 was corroborated by electrochemical measurements and calculation of Delta ETGo for PET, and (time-dependent) density functional theory computations. This less frequently encountered quenching mechanism where the BODIPY is an electron donor provides new opportunities in the rational design of new generations of fluorescent sensors. The applicability for intracellular measurements was demonstrated by confocal fluorescence microscopy on H460 human cancer cell line.

Arginine, due to the guanidine moiety, increases peptides’ hydrophilicity and enables interactions with charged molecules, but at the same time, its presence in a peptide chain might reduce its permeability through biological membranes. This might be resolved by temporary coverage of the peptide charge by lipophilic, enzyme-sensitive alkoxycarbonyl groups. Unfortunately, such a modification of a guanidine moiety has not been reported to date and turned out to be challenging. Here, we present a new, optimized strategy to obtain arginine building blocks with increased lipophilicity that were successfully utilized in the solid-phase peptide synthesis of novel arginine vasopressin prodrugs.

Human neurohormone vasopressin (AVP) is synthesized in overlapping regions in the hypothalamus. It is mainly known for its vasoconstricting abilities, and it is responsible for the regulation of plasma osmolality by maintaining fluid homeostasis. Over years, many attempts have been made to modify this hormone and find AVP analogues with different pharmacological profiles that could overcome its limitations. Non-peptide AVP analogues with low molecular weight presented good affinity to AVP receptors. Natural peptide counterparts, found in animals, are successfully applied as therapeutics; for instance, lypressin used in treatment of diabetes insipidus. Synthetic peptide analogues compensate for the shortcomings of AVP. Desmopressin is more resistant to proteolysis and presents mainly antidiuretic effects, while terlipressin is a long-acting AVP analogue and a drug recommended in the treatment of varicose bleeding in patients with liver cirrhosis. Recently published results on diverse applications of AVP analogues in medicinal practice, including potential lypressin, terlipressin and ornipressin in the treatment of SARS-CoV-2, are discussed.

A concise and practical strategy towards a novel class of 14-membered macrocycles containing an enediyne (Z-3-ene-1,5-diyne) structural unit is described. A highly modular assembly of various precursors via sequential Ugi/Sonogashira reactions allowed the preparation of hybrid enediyne-peptide macrocycles in most cases as single diastereoisomers. Selected macrocyclic compounds showed moderate antiproliferative activity, and can be considered as templates suitable for further diversification in terms of ring size, shape, and stereochemistry.

Multicomponent reactions represent a highly efficient approach to a broad spectrum of structurally diverse compounds starting from simple and affordable compounds. A focused library of tweezers-like compounds is prepared by employing the multicomponent Passerini reaction comprising enediyne-derived amino aldehydes. The reaction proceeds under mild conditions yielding Passerini products in good to excellent yields. Postcondensation modifications of Passerini products are demonstrated through a simple deprotection/coupling approach comprising amino functionality, furnishing enediyne cores with highly decorated arms.

Two new adamantane anion receptors with amidopyrrole side arms were prepared and their anion binding ability in DMSO solutions with TBA salts (Cl-, AcO- and H2PO4-) was investigated by UV/Vis spectroscopy. After calculating the corresponding association constants of receptor-anion complexes, it became apparent that only one amidopyrrole side arm was engaged in complexation. These experimental findings were rationalized using computational tools and the binding mode was proposed. In addition to the found 1 : 1 stoichiometry, we showed that the studied receptors bind oxo-anions (H2PO4- and AcO-) more strongly than spherical halogenide (Cl-) anions.