Gennaro Pescitelli

Università di Pisa | UNIPI · Department of Chemistry and Industrial Chemistry

We synthesized bis-aryl carbazole borane derivatives having emissive properties and axial chirality. The resolution of a thermally stable atropisomeric pair (compound 1b), due to a B-C chiral axis, was achieved by chiral stationary-phase high-performance liquid chromatography (CSP-HPLC). Complete photophysical properties of all compounds were measu...

Focus on aggregate structure: thin‐film mapping by Synchrotron Radiation Electronic Circular Dichroism Imaging (SR‐ECDi) reveals multiple aggregation modes of chiral oligothiophenes in the solid state. Two oligothiophenes with the same conjugated skeleton and different chiral pendants lead to mesoscopic domains allied with different supramolecular...

The study of the chiroptical properties of thin‐film samples of two chiral benzo[1,2‐b:4,5‐b’]dithiophene‐based oligothiophenes with optoelectronic properties was carried out at Diamond B23 beamline using the synchrotron radiation electronic circular dichroism imaging (SR‐ECDi) facility. The experimental results support the hypothesis that the non‐...

Polyproline I helical structures are often considered as the hidden face of their most famous geminal sibling, Polyproline II, as PPI is generally spotted only within a conformational equilibrium. We designed and synthesized a stable Polyproline I structure exploiting the striking tendency of (S)-indoline-2-carboxylic acid to drive the peptide bond...

Chiral quinacridines react up to four times, step‐by‐step, with a‐diazomalonates under Ru(II) and Rh(II) catalysis. By selecting the catalyst, [CpRu(CH 3 CN) 3 ][PF 6 ] (Cp = cyclopentadienyl) or Rh 2 (oct) 4 , chemo and regioselective insertions of derived metal carbenes are achieved in favor of mono‐ or bis‐functionalized malonate derivatives res...

A bioactive disubstituted nonenolide, named truncatenolide, was produced by Colletotrichum truncatum, which was collected from infected tissues of soybean showing anthracnose symptoms in Argentina. This is a devastating disease that drastically reduces the yield of soybean production in the world. The fungus also produced a new trisubstituted oct-2...

The study of chiroptical properties in thin films of chiral organic π‐conjugated dyes is more complex than isotropic solutions, due to the interference of macroscopic anisotropies often present in the solid state. The experimental circularly polarized (CP) absorption (electronic circular dichroism, ECD) and CP emission (circularly polarized lumines...

Chiral quinacridines react chemo- and regioselectively with α-diazomalonates under RuII/RhII catalysis, up to four times, achieving a stepwise late-stage multi-functionalization of the [4]helicene scaffold. Absorption, emission or Brønsted acidity but also cellular bioimaging are readily tuned. Density-functional theory elucidates the carbene inser...

A family of bis[(R or S)‐N‐1‐(Ar)ethylsalicylaldiminato‐κ2N,O]‐Δ/Λ‐zinc(II) {Ar=C6H5 (ZnRL1 or ZnSL1), p‐CH3OC6H4 (ZnRL2 or ZnSL2) and p‐ClC6H4 (ZnRL3 or ZnSL3)} compounds was synthesized and investigated by multiple methods. They feature Λ/Δ‐chirality‐at‐metal induction along the pseudo‐C2 axis of the molecules. The chirality induction is quantita...

The chiroptical features of chiral diketopyrrolo[3,4‐ c ]pyrrole (DPP) derivatives have been only marginally investigated to date. In this regard, we have synthesized ad hoc four chiral DPP dyes, functionalized with enantiopure alkyl groups from natural sources either on the lactam moieties or on the terminal positions of π‐conjugated backbone, to...

Novel chiral Er complexes based on both enantiomers of extended iPrPyBox (2,6‐Bis[4‐isopropyl‐4,5‐dihydrooxazol‐2‐yl)]pyridine) show strong near‐infrared circularly polarized luminescence (CPL) within the 1400 to 1600 nm spectral region under 450 nm irradiation. CPL activity in this region, despite being particularly rare, would open the way to pot...

Novel chiral Er complexes based on both enantiomers of extended iPrPyBox (2,6‐Bis[4‐isopropyl‐4,5‐dihydrooxazol‐2‐yl)]pyridine) show strong near‐infrared circularly polarized luminescence (CPL) within the 1400 to 1600 nm spectral region under 450 nm irradiation. CPL activity in this region, despite being particularly rare, would open the way to pot...

Solid-state ECD (ss-ECD) spectra of a model microcrystalline solid, finasteride, dispersed into a KCl pellet were recorded by using the synchrotron radiation source at the Diamond B23 beamline. Scanning a surface of 36 mm2 with a step of 0.5 mm, we measured a set of ECD imaging (ECDi) spectra very different from each other and from the ss-ECD recor...

Thanks to the concept of synchrotron radiation ECD imaging (SR-ECDi) applied to the active pharmaceutical ingredient Finasteride, we obtained an exclusive insight into the critical role played by the anisotropy of local domains in solid-state ECD spectra. Our findings open a new way to interpret solid-state chiroptical measurements and will broaden...

Organic compounds showing circularly polarized luminescence (CPL) are at the forefront of novel applications and technologies. Here we show the synthesis and chiroptical properties of pyrene and perylene derivatives of inexpensive chiral scaffolds: isomannide and isosorbide. Low-intensity ECD spectra were obtained, suggesting the absence of chromop...

We carried out a study of absorption (CD) and emission (CPL) chiroptical properties in the NIR region of two sets of Yb, Tm and Er complexes. The two complexes include a D3 symmetric, [TMG-H+]3Ln(BINOLate)3 (Ln = Yb, Tm, Er; TMG = 1,1,3,3-tetramethylguanidine; BINOLate = 1,1'-bi-2-naphtholate), and a tetrakis, C4 symmetric, CsLn(hfbc)4 (Ln = Yb, Tm...

The application of the exciton chirality method (ECM) to interpret electronic circular dichroism (ECD) spectra is a well‐established and still popular approach to assign the absolute configuration (AC) of natural products, chiral organic compounds, and organometallic species. The method applies to compounds containing at least two chromophores with...

Angucyclines and angucyclinones represent the largest family of type II PKS-engineered natural products. Chemical analysis of a marine Streptomyces sp. KCB-132 yielded three new members, actetrophenone A (1) and actetrophenols A–B (2–3). Their structures were elucidated by NMR spectroscopy, X-ray crystallography and CD calculations. Actetrophenone...

The enantiopure Schiff bases (R or S)-N-1-(X-C6H4)ethyl-2-hydroxy-1-naphthaldimine {X = H [(R or S)-HL1], p-CH3O [(R or S)-HL2], and p-Br [(R- or S)-HL3]} react with cobalt(II) acetate to give bis[(R or S)-N-1-(X-C6H4)ethyl-2-oxo-1-naphthaldiminato-κ²N,O]-Λ/Δ-cobalt(II) {X = H [Λ/Δ-Co-(R or S)-L1], p-CH3O [Λ/Δ-Co-(R or S)-L2], and p-Br [Λ/Δ-Co-(R o...

We report the asymmetric synthesis of homochiral metal–organic materials (MOMs) in chiral gels from achiral components. The enantioselectivity of MOMs depends on the chirality of the gel, whereas the synthesis performed in solution phase and achiral gels resulted in conglomerates. Asymmetric synthesis of MOMs in gels: Gel phase synthesis of metal–o...

Asymmetric synthesis of MOMs in gels: Gel phase synthesis of metal–organic materials (MOMs) resulted in homochiral MOMs, which were characterized by single crystal X-ray diffraction. The chirality of the gelator dictated the handedness of the MOMs and the enantioselectivity was confirmed by solid-state circular dichroism experiments. Abstract We r...

Four racemic iminoflavan derivatives were synthesized by simple condensation at C‐4 position of flavanone. All new compounds were characterized by using ultraviolet‐visible, infrared and nuclear magnetic resonance spectroscopic techniques. A chiral chromatographic analysis of racemic mixtures was performed by direct chiral high‐performance liquid c...

A thorough experimental and computational study on the conformational properties of (S)-indoline-2-carboxylic acid derivatives has been conducted. Methyl (S)-1-acetylindoline-2-carboxylate, both a mimetic of proline and phenylalanine, shows a remarkable tendency toward the cis amide isomer when dissolved in polar solvents. This behavior is opposite...

A new cleistanthane nor-diterpenoid, named olicleistanone (1), was isolated as a racemate from the culture filtrates of Diplodia olivarum, an emerging pathogen involved in the aetiology of branch canker and dieback of several plant species typical of the Mediterranean maquis in Sardinia, Italy. When the fungus was grown in vitro on Czapek medium, o...

Two new penta- and tetrasubstituted cyclopentenones, named phaseocyclopentenones A and B (1 and 2), together with guignardone A (3), were isolated from Macrophomina phaseolina cultures. The phytopathogenic fungus was isolated from infected soybean tissues showing charcoal rot symptoms in Argentina. Charcoal rot is a devastating disease considering...

New bis-quinolinium chiral ionic liquids (CILs) were synthesized in good yields starting from isomannide and isosorbide by a straightforward procedure that maintains the absolute stereostructure of the isohexide scaffolds. Thermal gravimetric analysis and differential scanning calorimetry, aimed at investigating the short thermal stability and the...

Chiral π-conjugated molecules provide new materials with outstanding features for current and perspective applications, especially in the field of optoelectronic devices. In thin films, processes such as charge conduction, light absorption, and emission are governed not only by the structure of the individual molecules but also by their supramolecu...

Controlling circularly polarized (CP) emission is key for both fundamental understanding and applications in the field of chiral photonics and electronics. Here, a completely new way to achieve this goal is presented. A luminescent thin film, made from a chiral conjugated phenylene bis‐thiophenylpropynone able to self‐assemble into ordered structur...

A new cleistanthane nor -diterpenoid, named olicleistanone (1), was isolated as a racemate from the culture filtrates of Diplodia olivarum an emerging pathogen involved in the aetiology of branch canker and dieback of in several plant species typical of the Mediterranean maquis in Sardinia, Italy. When the fungus was grown in vitro on Czapek medium...

Ganorbifate A featuring an unprecedented 6/6/6/5/5 pentacyclic system, and ganorbifate B with an unusual 6/4/6/5/8/5 ring system were isolated from the fruiting body of Ganoderma orbiforme. Their structures were established...

A series of novel 1,4-dioxane analogs of the muscarinic acetylcholine receptor (mAChR) antagonist 2 was synthesized and studied for their affinity at M1-M5 mAChRs. The 6-cyclohexyl-6-phenyl derivative 3b, with a cis configuration between CH2N+(CH3)3 chain in the 2-position and the cyclohexyl moiety in 6-position, showed pKi values for mAChRs higher...

Colletotrichum lupini: is the causal agent of lupin (Lupinus albus L.) anthracnose, a destructive seed-borne disease affecting stems and pods. Despite that several biological studies have been carried out on this pathogen, the production of secondary metabolites has not yet been investigated. Thus, a strain of C. lupini, obtained from symptomatic...

The synthesis of a chiral tetraarylmethane derivative is reported. The solvent effect on the CD spectra was observed for the solution. This is attributable to a molecular design with three of four aryl groups have the nitrogen atom at the ortho position with respect to the central carbon atom. This unique design was realized when a variety of trans...

Two new diterpenoids with tetrasubstituted 3-oxodihydrofuran substituents, named higginsianins D (1) and E (2), were isolated from the mycelium of the fungus Colletotrichum higginsianum grown in liquid culture. They were characterized as methyl 2-[6-hydroxy-5,8a-dimethyl-2-methylene-5-(4-methylpent-3-enyl)-decahydronaphthalen-1-ylmethyl]-4,5-dimeth...

Moving from the simple concept that reflection onto a mirror surface changes the handedness of circularly polarized light, we describe what happens to the emergent polarization in two different cases after reflection on a back mirror. In the first case, a regular emitter is taken into account, where reflection has the effect to destroy the emergent...

Phenyl‐pyrazinyl‐2‐pyridyl‐2‐pyrimidinylmethane (1) has been synthesized in four steps from 2‐(chloromethyl)pyridine. This compound is chiral and expected to show the metal coordinating ability because three of four aryl groups have the nitrogen atom at ortho‐position with respect to the central carbon atom. The X‐ray crystallographic analysis of r...

(±)‐Pratenone A (1), the first representative of natural 3‐(1‐naphthyl)‐2‐benzofuran‐1(3H)‐one polyketides, was isolated from a marine‐derived Streptomyces pratensis strain KCB‐132 together with three other new analogues (2−4). Its structure was assigned by spectroscopic analysis, and the absolute configurations of the two enantiomers separated by...

A new phytotoxic tetrasubstituted chromen-4-one (1) and a new hexasubstituted benzophenone (2), named rabenchromenone and rabenzophenone, respectively, were isolated from the culture filtrates of Fimetariella rabenhorstii, an oak-decline-associated fungus in Iran. Rabenchromenone and rabenzophenone, isolated together with known moniliphenone (3) an...

Different phytotoxic metabolites were isolated from the organic extract of Neofusicoccum luteum, Neofusicoccum australe, and Neofusicoccum parvum, causal agents of Botryosphaeria dieback in Australia. N. luteum produced a new disubstituted furo-α-pyrone, a hexasubstituted anthraquinone, and a trisubstituted oxepi-2(7H)-one, luteopyroxin (4), neoant...

A series of oligomers containing alternate L-Ala and pGlu (pyroglutamic acid) both in the L and D form have been prepared and conformationally investigated by X-ray, NMR, UV/ECD, IR/VCD and molecular modelling. X-ray diffraction analysis was possible for the shortest oligomers LL-1 and LD-1. Molecular dynamics simulations of the oligomers demonstra...

A new tetranorditerpenoid (1), two new labdane diterpenoids (2, 3), and nine known analogues (4-12) were isolated from the rhizomes of Amomum villosum var. xanthioides. Compound 1 is an unprecedented rearranged tetranorlabdane diterpenoid, featuring a 6/6/5 fused tricarbocyclic skeleton with an α,β-unsaturated cyclopentenone unit, while 2 is a stru...

We demonstrated the hitherto unknown property of the mycotoxin sterigmatocystin (STC) to provide homogeneous solutions in aqueous medium by forming a unique aggregate type (not formed by analogous aflatoxins), characterized by exceptionally strong circular dichroism (CD) bands in the 300-400 nm range. Results showed that these CD bands do not origi...

The chiral spin–flip luminophore [Cr(ddpd) 2 ] ³⁺ can be resolved into enantiopure material by chiral HPLC. The pure enantiomers display strong CPL activity for the corresponding near-IR phosphorescence.

We highlight the power of electronic circular dichroism imaging (CDi), a technique developed at Diamond Light Source B23 beamline for synchrotron radiation circular dichroism (SRCD) to detect local domains of chiral supramolecular order in thin films of chiral oligomers and polymers. The highly brilliant and collimated beamlight of B23 enabled CDi...

The direct heterofunctionalization of acyclic α,β‐unsaturated aldehydes with N‐acylquinolinium ions contemplating the formation of two stereocentres is studied using dienamine catalysis. This work gives some new experimental insights on the remote stereocontrol in dienamine catalysis using unbiased aliphatic systems and large electrophiles, pointin...

Bioactivity-guided isolation of the cultures of the endophytic fugus Xylaria sp. XC-16 residing in a deciduous tree Toona sinensis led to the discovery of four new allelochemicals (1–4) including three cytochalasins, epoxycytochalasin Z17 (1), epoxycytochalasin Z8 (2), epoxyrosellichalasin (3), and an abietane-type diterpenoid, hydroxyldecandrin G...

A fruitful switch from tert-butyl to cumene hydroperoxide was able to overcome a difficulty arose in the enantioselective oxidation of fluorinated aryl benzyl sulfide with hydroperoxides in the presence of a titanium/(S, S)-hydrobenzoin catalyst. New experiments show the complementarity of the old and the new protocols and indicate unequivocally th...

Tolterodine (1) is a potent muscarinic receptor antagonist used in the treatment of overactive urinary bladder (OAB) syndrome. Tolterodine is chiral and it was patented, and is currently marketed, as the l-tartrate salt of the (R)-enantiomer. However, the existing literature does not offer an ultimate proof of a stereoselective mode of action of 1....

Chiral coordination compounds of Co(II) and other metal ions with low-lying excited states (LLES) display enhanced vibrational circular dichroism (VCD) spectra which can be used for sensing purposes. In addition to the enhancement, a series of Co(II) salicylaldiminato complexes exhibit unique VCD spectra which are almost monosignate, instead of sho...

The direct catalytic α‐amidoalkylation of dihydroquinolines with aldehydes bearing oxygen functionalities at different positions in a Mannich‐type reaction has been studied. β‐Alkoxy‐aldehyde 1d gave high enantioselectivity, albeit with an inherently poor diastereoselectivity, while the use of α‐alkoxy aldehydes 1c was detrimental also to enantiose...

A strain of the pathogenic fungus Ascochyta lentis isolated from lentil ( Lens culinaris) was studied to ascertain its capability to produce bioactive metabolites. From the culture filtrates were found three new anthraquinone derivatives, named lentiquinones A (1), B (2), and C (3), and the known lentisone. From the mycelium, four known analogues w...

Chiroptical broad-range spectral analysis extending from UV to mid-IR was employed to study a family of Co(II) N-(1-(aryl)ethyl)salicylaldiminato Schiff base complexes with pseudotetrahedral geometry associated with chirality-at-metal of the Δ/Λ type. While common chiral organic compounds have well-separated absorption and circular dichroism spectr...

The bis carbene gold(I) complex [Au(1-butyl-3-methyl-2-ylidene)2]PF6, ([Au(NHC)2]PF6 hereafter), holds remarkable interest as a perspective anticancer agent. The compound is stable under physiological like conditions: its original structure is retained even in the presence of excess glutathione (GSH). Previous studies revealed its high cytotoxicity...

The circular dichroism (CD) exciton chirality method (ECM) is a very popular approach for assigning the absolute configuration (AC) of natural products, thanks to its immediacy and ease of application. The sign of an exciton couplet (two electronic CD bands with opposite sign and similar intensity) can be directly correlated with the molecular ster...

Straightforward synthesis and resolution of a series of chiral fluorescent macrocycles are presented, together with their electronic circular dichroism (ECD), strong excimer fluorescence (EF, λ 300 to 650 nm) and allied highly circularly polarized luminescence (CPL, glum up to 1.7×10⁻²). The ECD, EF and CPL responses are strongly affected by the pr...

We simulate the vibronic profile of the electronic circular dichorism (ECD) spectra of oligothiophenes in cisoid and transoid chiral arrangements. We consider oligomers of different lenghts, from two to fifteen units, and investigate extensively how the ECD spectral shapes depend on the inter-ring torsions. In general, the molecular structures we c...

A fungal pathogen soon to be described as Rutstroemia capillus-albis (Rutstroemiaceae, Helotiales, Leotiomycetes) has been identified as the causal agent of ‘bleach blonde syndrome’ on the invasive annual grass weed Bromus tectorum (cheatgrass) in western North America. This apparently common but previously undescribed disease causes premature sene...

An enantioselective electrophilic amination of 3-substituted-2-oxindoles is reported, using bis(2,2,2-trichloroethyl)azo-dicarboxylate and commercially available Cinchona alkaloid organocatalysts. The best results were obtained in the reaction of 3-aryl substrates, with high to excellent yields (75% to quantitative) and good stereoselectivity (64–7...

A helicate placed in front of a mirror returns the specular image with opposite helicity, whereas the mesocates lack this property. By playing with the torsion angles of the central spacer of a series of Schiff bases with different substituents on the C atoms and the size of the aromatic groups, controlled transition between the two conformations h...

A helicate placed in front of a mirror returns the specular image with opposite helicity, whereas the mesocates lack this property. By playing with the torsion angles of the central spacer of a series of Schiff bases with different substituents on the C atoms and the size of the aromatic groups, controlled transition between the two conformations h...

Kiamycins B (1) and C (2), two unusual angucyclinones bearing a novel 6,12-epoxybenz[a]anthracene ring system, were isolated from the cultures of a marine sediment-derived Streptomyces sp. along with one structurally related derivative 3. Their structures and stereochemistries were determined by spectroscopic analyses, single-crystal X-ray diffract...

From the culture filtrates of Diaporthella cryptica, an emerging hazelnut pathogen, 2-hydroxy-3-phenylpropanoate methyl ester and its 3-(4-hydroxyphenyl) and 3-(1H-indol-3-yl) analogues, named crypticins A-C, were isolated together with the well-known tyrosol. Crypticins A-C were identified by spectroscopic (essentially NMR and HRESI MS) methods. T...

Ten schinortriterpenoids with biogenetically related lancischiartane scaffolds, including the first 3-norlancischiartane (1) with unusual configuration inversions occurring at C-1 and C-10, were isolated from Schisandra lancifolia. Unusual ECD curve patterns observed in 6–8 were confirmed to be caused by nondegenerate exciton coupling, suggesting t...

The systematic reactions of a family of tetradentate pyridyl/imine and quinolyl/imine racemic or enantiopure Schiff bases with Ni(NO3)2 or Ni(ClO4)2 in the presence of sodium azide yielded, as a function of the starting racemic, chiral or achiral base, a set of chiral, meso or achiral complexes. In all cases, the compounds consist in two NiII catio...

In a previous study, we reported ten new polyoxygenated cyathane diterpenoids, neocyathins A-J, and their anti-neuroinflammatory effects from the liquid culture of the medicinal Basidiomycete Cyathus africanus. In the present study, eight new highly polyoxygenated cyathane diterpenoids, named neocyathins K-R (1-8), were isolated from the solid cult...