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[EN] The main goal of the present work was to investigate the damages photoinduced by pterin (Ptr), an endogenous photosensitizer present in human skin under pathological conditions, on a globular protein such as ubiquitin (Ub). Particular attention has been paid on the formation of covalent adducts between Ptr and the protein that can behave as photoantigen and provoke an immune system response. Here, a multifaceted approach including UV-visible spectrophotometry, fluorescence spectroscopy, electrophoresis, size exclusion chromatography, and mass spectrometry is used to establish the Ub changes triggered by UV-A irradiation in the presence of Ptr. Under anaerobic conditions, the only reaction corresponds to the formation of a covalently bound Ptr-Ub adduct that retains the spectroscopic properties of the free photosensitizer. A more complex scheme is observed in air-equilibrated solutions with the occurrence of three different processes, that is, formation of a Ptr-Ub adduct, dimerization, and fragmentation of the protein., The present work was partially supported by Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET-Grants PIP 112-200901-0304 and PIP 11220120100072CO), Agencia de Promocion Cientifica y Tecnologica (ANPCyT-Grants PICT-2015-1988 and PICT 2016-00130), Universidad Nacional de La Plata (UNLP-Grant X712 and X840), and Universidad de Buenos Aires (UBA-Grant 000110BA). Funding from the Programa CSIC de Cooperacion Cientifica para el Desarrollo (iCOOPLight project ref 20105CD0017) and Spanish government (PGC2018-096684-B-I00) is gratefully acknowledged. The Ultraflex II (Bruker) TOF/TOF mass spectrometer was supported by a grant from ANPCYT, PME2003 No. 125, and the ESI-MS Q Exactive, Thermo Scientific, by a grant from ANPCYT, PME2011-PPL2-0009, CEQUIBIEM, DQB, FCEN, UBA. The proteomic analysis was performed in the proteomics facility of SCSIE University of Valencia. This proteomics laboratory is a member of Proteored, PRB3 and is supported by grant PT17/0019, of the PE I+D+i 2013-2016, funded by ISCIII and ERDF. L.O.R. thanks CONICET for doctoral research fellowships. RE-B, G.P., M.L.D., and A.H.T are research members of CONICET.

[EN] In this work, the attention is focused on UVA-photosensitized reactions triggered by a DNA chromophore-containing lesion, namely 5-formyluracil. This is a major oxidatively generated lesion that exhibits an enhanced light absorption in the UVB-UVA region. The mechanistic study combining photochemical and photobiological techniques shows that irradiation of S-formyluracil leads to a triplet excited state capable of sensitizing formation of cyclobutane pyrimidine dimers in DNA via a triplet-triplet energy transfer. This demonstrates for the first time that oxidatively generated DNA damage can behave as an intrinsic sensitizer and result in an important extension of the active fraction of the solar spectrum with photocarcinogenic potential. Overall, this raises the question of an aggravated photomutagenicity of the 5-formyluracil lesion., The present work was supported by Spanish Government (CTQ2015-70164-P, Severo Ochoa program/SEV-2012-0267, BES-2013-066566, CSIC 2016801007), Instituto de Salud Carlos III (RD16/0006/0030, FIS PI16/01877), Generalitat Valenciana (Prometeo/2017/075).

[EN] The photoreactivity of fenofibric acid (FA) in the presence of human and bovine serum albumins (HSA and BSA, respectively) has been investigated by steady-state irradiation, fluorescence, and laser flash photolysis (LFP). Spectroscopic measurements allowed for the determination of a 1:1 stoichiometry for the FA/SA complexes and pointed to a moderate binding of FA to the proteins; by contrast, the FA photoproducts were complexed more efficiently with SAs. Covalent photobinding to the protein, which is directly related to the photoallergic properties of the drug, was detected after long irradiation times and was found to be significantly higher in the case of BSA. Intermolecular FA-amino acid and FA-albumin irradiations resulted in the formation of photoproducts arising from coupling between both moieties, as indicated by mass spectrometric analysis. Mechanistic studies using model drug-amino acid linked systems indicated that the key photochemical step involved in photoallergy is formal hydrogen atom transfer from an amino acid residue to the excited benzophenone chromophore of FA or (more likely) its photoproducts. This results in the formation of caged radical pairs followed by C-C coupling to give covalent photoaducts., Financial support from the Spanish Government (CTQ2013-47872-C2-1-P, JCI-2011-09926, and Miguel Servet CP11/00154), EU (PCIG12GA-2012-334257) and Generalitat Valenciana (PROMETEOII/2013/005) is gratefully acknowledged.

[EN] Discovered more than eight decades ago, the Diels-Alder (DA) cycloaddition (CA) remains one of the most versatile tools in synthetic organic chemistry. Hetero-DA processes are powerful methods for the synthesis of densely functionalized six-membered heterocycles, ubiquitous substructures found in natural products and bioactive compounds. These reactions frequently employ azadienes and oxadienes, but only a few groups have reported DA processes with thiadienes. The electron transfer (ET) version of the DA reaction, though less investigated, has emerged as a subject of increasing interest. In the last two decades, researchers have paid closer attention to radical ionic hetero-cycloreversions, mainly in connection with their possible involvement in the repair of pyrimidine(6-4)pyrimidone photolesions in DNA by photolyases. In biological systems, these reactions likely occur through a reductive photosensitization mechanism. In addition, photooxidation can lead to cycloreversion (CR) reactions, and researchers can exploit this strategy for DNA repair therapies. In this Account, we discuss electron-transfer (ET) mediated hetero-CR reactions. We focus on the oxidative and reductive ET splitting of oxetanes, azetidines, and thietanes. Photoinduced electron transfer facilitates the splitting of a variety of four-membered heterocycles. In this context, researchers have commonly examined oxetanes, both experimentally and theoretically. Although a few studies have reported the cycloreversion of azetidines and thietanes carried out under electron transfer conditions, the number of examples remains limited. In general, the cleavage of the ionized four-membered rings appears to occur via a nonconcerted two-step mechanism. The trapping of the intermediate 1,4-radical ions and transient absorption spectroscopy data support this hypothesis, and it explains the observed loss of stereochemistry in the products. In the initial step, either C-C or C-X bond breaking may occur, and the preferred route depends on the substitution pattern of the ring, the type of heteroatom, and various experimental conditions. To better accommodate spin and charge, C-X cleavage happens more frequently, especially in the radical anionic version of the reaction. The addition or withdrawal of a single electron provides a new complementary synthetic strategy to activate hetero-cycloreversions. Despite its potential, this strategy remains largely unexplored. However, it offers a useful method to achieve C=X/olefin metathesis or, upon ring expansion, to construct six-membered heterocyclic rings., Financial support from the Spanish Government (Grants CTQ2010-14882, SEV2012-0267, and JCI-2010-06204) and the Generalitat Valenciana (Prometeo II/2013/005) is gratefully acknowledged.

Photolysis of the benzophenone chromophore by means of high energy laser pulses has been used as a tool to populate upper thymine-like triplet states via intramolecular sensitization. These species undergo characteristic n pi* photoreactivity, as revealed by the Norrish-Yang photocyclization of 5-tert-butyluracil., Financial support by the Spanish government (CTQ2009-13699, CTQ2012-32621, RyC-2007-00476 to V.L.-V. and JAE-Predoc 2011-00740 contract to V.V.-C.) and the Generalitat Valenciana (Prometeo program) is gratefully acknowledged. M.Y, is thankful for Grants-in-Aid for Scientific Research (KAKENHI) from JSPS (No. 23350059) and the "Element Innovation" Project by the Ministry of Education, Culture, Sports, Science, and Technology, Japan.

A new direct and noninvasive methodology based on transient absorption spectroscopy has been developed to probe the feasibility of drug-drug interactions within a common protein binding site. The simultaneous presence of (R)-cinacalcet (CIN) and (S)-propranolol (PPN) within human or bovine alpha(1)-acid glycoproteins (AAGs) is revealed by detection of (CIN)-C-3* as the only transient species after laser flash photolysis of CIN/PPN/AAG mixtures at 308 nm. This is the result of triplet-triplet energy transfer from (PPN)-P-3* to CIN, which requires close contact between the two drugs within the same biological compartment. Similar results are obtained with nabumetone and CIN as donor/acceptor partners. This new methodology can, in principle, be extended to a variety of drug/drug/biomolecule combinations., Financial support from the Spanish Government (CTQ2009-13699, CTQ2010-14882) and from the Carlos III Institute of Health (Grant RIRAAF, RETICS program, and Miguel Servet Contract CP11/00154 for I.A.) is gratefully acknowledged.

Reductive photodehalogenation of chloroaromatics is assumed to proceed from the triplet excited state, although its energy is often insufficient to promote a clean homolytic C¿Cl cleavage. A clear-cut experimental proof is provided that correlates self-quenching of the directly observed triplet excited states of chlorocarbazole-based dyads 1 and 2 with photoreactivity via intramolecular charge transfer., Financial support from the Spanish Government (CTQ2010-14882, BES-2011-043706, JCI-2010-06204) and from the Generalitat Valenciana (Prometeo 2008/090 and GV/2012/041) is gratefully acknowledged.

Excited-state interactions between (S)- or (R) fluorescence (S)- or (R)-FBP) and thymidine (dThd) covalently linked in dyads 1 or 2 have been investigated. In both dyads, the only emitting species is (FBP)-F-1*, but with a lower fluorescence quantum yield (phi(F)) and a shorter fluorescene lifetime (tau(F)) than when free in solution. These an results indicate that dynamic quenching occurs either by electron transfer or via exciplex formation, with FBP as the charge-donating species. In acetonitrile, both mechanisms are favored, while in dioxane exciplex formation is predominating. Isomer 1 displays lower values of OF and rF than its analogue 2, indicating that the relative spatial arrangement of the chromophores plays a significant role. The triplet quantum yields (0-F) of 1 and 2 are significantly higher than the expectations based solely on 'FBP* dThd intersystem crossing quantum yields (Oisc), with OT (1) > OT (2). This can be explained in terms of intramolecular charge recombination at the radical ion pairs and/or the exciplexes, which would be again dependent on geometrical factors. The triplet lifetimes (IT) of 3FBP* dThd and free 3FBP* are similar, indicating the lack of excited-state interactions at this stage. The FBP dThd dyads could, in principle, constitute appropriate model systems for the elucidation of the excited-state interactions in noncovalent DNA ligand complexes., Financial support from the Spanish Government (Grants CTQ2010-14882 and CTQ2009-13699), Salvador Madariaga Program (Grant to M.C.J.), Juan de la Cierva Program (contract to I.V.), Generalitat Valenciana (Prometeo 2008/090), and the Universitat Politecnica de Valencia (PAID 05-11, ref 2766) is gratefully acknowledged.

In this work, the triplet state behavior of naphthalene-based pseudopeptides with amide-based macrocyclic or lateral chain substructures has been investigated in the presence of benzophenone and/or biphenyl, as suitable energy donating chromophores. Their behavior has been compared with that of 1,4-dimethylnaphthalene as model compound.,,In all the cases,. the triplet-triplet absorption of naphthalene is detected by transient absorption spectroscopy, upon selective excitation of benzophenone at 355 nm. The kinetics of formation and decay of this species is markedly slower in the pseudopeptides, due to retardation of triplet-triplet energy transfer and exciplex formation. Finally, the delayed fluorescence detected in the model naphthalene is absent in the pseudopeptides. The concept can, in principle, be exploited for the study of excited state interactions. in supramolecular systems, Financial support from the MICINN (Grants CTQ-2010-14882, CTQ2009-14366-C02-01 and FPI contract to P.B.), the Generalitat Valenciana (Prometeo 2008/090), the UPV (PAID 05-11 Program, ref 2766), and Fundacio Caixa Castello-UJI (P1 1B-2009-59) is gratefully acknowledged.

Bile acids (BAs) are a family of natural steroids biosynthesized from cholesterol in the liver that tend to form aggregates in solution. A fluorescent derivative of cholic acid, namely 3 alpha-Dns-ChA, was employed as a reporter to establish the speciation diagrams of the most abundant BAs that can be found mainly in three microenvironments, solution, and primary and secondary aggregates. The developed methodology is based on the analysis of the combined steady-state and time-resolved experiments performed on 3 alpha-Dns-ChA whose emission behavior was found to be strongly medium dependent. In particular, speciation diagrams of sodium glycocholate (NaGCh), sodium taurocholate (NaTCh), sodium chenodeoxycholate (NaCDCh), sodium glycochenodeoxycholate (NaGCDCh), sodium deoxycholate (NaDCh), and sodium ursodeoxycholate (NaUDCh) were successfully built up. © 2012 American Chemical Society., We gratefully acknowledge financial support from the Generalitat Valenciana (GV/2009/104 and Prometeo 2008/090), the Spanish Government (Red RETICS de Investigacion de Reacciones Adversas a Alergenos y Farmacos (RIRAAF), CTQ2009-13699, and Predoctoral FPU fellowship AP2008-03295 for M.G.-M.).

The use of organic photocatalysts for the oxidation of pollutants and model compounds, with special emphasis on the involved concepts and mechanistic aspects, is reviewed. Photoinduced electron transfer involving the singlet excited state of phthalocyanines has been postulated in the photodegradation of phenols. The reactivity of OH - radical with different pollutants has been quantitatively determined by competition experiments, looking at the decrease of the typical transient absorption of the stilbene adduct at 390 nm. As regards heterogeneous media, after excitation at 355 nm of phthalocyanines immobilized in zeolites, the characteristic singlet oxygen luminiscence is monitored at 1270 nm. TPP has been included within extralarge pore zeolitic aluminosilicates, such as MCM-41. These materials provide an adequate balance between moderate cage effect and facilitation of molecular traffic through the mesopores., Financial support from the Spanish Government (CTQ2009- 13699, CTQ2009-13459-C05-03/PPQ, RIRRAF RETICS), and the Generalitat Valenciana (Prometeo Program) is gratefully acknowledged. Dedicated to Prof. Avelino Corma on the occasion of his 60th birthday.

[EN] A lthough the carcinogenic potential of ultraviolet radiation is well-known, UV light may interact with DNA by direct absorption or through photosensitization by endogenous or exogenous chromophores. These chromophores can extend the ¿active¿ fraction of the solar spectrum to the UVA region and beyond, which means that photosensitizers increase the probability of developing skin cancer upon exposure to sunlight. Therefore researchers would like to understand the mechanisms involved in photosensitized DNA damage both to anticipate possible photobiological risks and to design tailor-made photoprotection strategies. In this context, photosensitized DNA damage can occur through a variety of processes including electron transfer, hydrogen abstraction, triplet triplet energy transfer, or generation of reactive oxygen species. In this Account, we have chosen benzophenone (BP) as a classical and paradigmatic chromophore to illustrate the different lesions that photosensitization may prompt in nucleosides, in oligonucleotides, or in DNA. Thus, we discuss in detail the accumulated mechanistic evidence of the BP-photosensitized reactions of DNA or its building blocks obtained by our group and others. We also include ketoprofen (KP), a BP-derivative that possesses a chiral center, to highlight the stereodifferentiation in the key photochemical events, revealed through the dynamics of the reactive triplet excited state (3KP*). Our results show that irradiation of the BP chromophore in the presence of DNA or its components leads to nucleobase oxidations, cyclobutane pyrimidine dimer formation, single strand breaks, DNA protein cross-links, or abasic sites. We attribute the manifold photoreactivity of BP to its well established photophysical properties: (i) it absorbs UV light, up to 360 nm; (ii) its intersystem crossing quantum yield (OISC) is almost 1; (iii) the energy of its n¿* lowest triplet excited state (ET) is ca. 290 kJ mol 1; (iv) it produces singlet oxygen (1O2)with a quantum yield (¿¿) of ca. 0.3. For electron transfer and singlet oxygen reactions, we focused on guanine, the nucleobase with the lowest oxidation potential. Among the possible oxidative processes, electron transfer predominates. Conversely, triplet triplet energy transfer occurs mainly from 3BP* to thymine, the base with the lowest lying triplet state in DNA. This process results in the formation of cyclobutane pyrimidine dimers, but it also competes with the Patern o B¿uchi reaction in nucleobases or nucleosides, giving rise to oxetanes as a result of crossed cycloadditions. Interestingly, we have found significant stereodifferentiation in the quenching of the KP triplet excited state by both 20-deoxyguanosine and thymidine. Based on these results, this chromophore shows potential as a (chiral) probe for the investigation of electron and triplet energy transport in DNA., We thank our co-workers who contributed to this research whose names appear in the references. Financial support from the Spanish Government (Grant CTQ2009-13699, JAE Doc fellowship for M.C.C, and Ramon y Cajal contract for V.L.-V.) is gratefully acknowledged.

The two enantiomers of 2-(2-hydroxybiphenyl-4-yl)propanoic acid ((S)- and (R)-BPOH) have been selected as probes for human serum albumin (HSA). Photophysical characterization in the absence of protein led to emission maxima, singlet energies, quantum yields, and fluorescence lifetime values of 332 nm, 91 kcal mol(-1), and 0.28 and 1.8 ns for BPOH or 414 nm, 79 kcal mol(-1), and 0.31 and 3.3 ns for the corresponding phenolate BPO-; the pK(a)* was found to be 1.17. In the presence of HSA, a light-absorbing ground-state complex (S)-BPOH@HSA was detected (maximum at ca. 300 nm) whose intensity increased with increasing protein concentration. The fluorescence spectra of (S)-BPOH in PBS, after addition of HSA, revealed a progressive diminution of the phenolate band, indicating that excited-state deprotonation is disfavored within the hydrophobic protein cavities. A similar trend was observed for (R)-BPOH, but the extent of deprotonation was significantly lower for this enantiomer. Addition of increasing amounts of the site II displacement probe (S)-ibuprofen ((S)-IBP) to BPOH@HSA led to a significant decrease of the absorption maximum at ca. 300 nm and to a recovery of the phenolate emission band at ca. 410 nm, which were again configuration dependent. The transient absorption spectrum of (S)-BPOH consisted on a broad band centered at 380 nm, attributed to the first triplet excited state. A dramatic enhancement of the triplet lifetimes within HSA was observed (19.0 mu s within protein versus 1.3 mu s in bulk PBS), although no stereodifferentiation was noticed in this case., Financial support from the Spanish Government (CTQ2010-14882, CTQ2009-13699, BES-2008-003314, JCI-2011-09926), from the Generalitat Valenciana (Prometeo 2008/090) and from the Universitat Politecnica de Valencia (PAID 05-11, 2766) is gratefully acknowledged.

In this work, rosuvastatin has been used to gain insight into the molecular basis of statin photosensitization. This lipid-lowering drug, also known as ¿superstatin¿, contains a 2-vinylbiphenyl-like moiety and has been previously described to decompose under solar irradiation, yielding stable dihydrophenanthrene analogues. During photophysical characterization of rosuvastatin, only a long-lived transient at ca. 550 nm was observed and assigned to the primary photocyclization intermediate. Thus, the absence of detectable triplet¿triplet absorption and the low yield of fluorescence rules out the role of the parent drug as an efficient sensitizer. In this context, the attention has been placed on the rosuvastatin main photoproduct (ppRSV). Indeed, the photobehavior of this dihydrophenanthrene-like compound presents the essential components needed for an efficient biomolecule photosensitizer i.e. (i) a high intersystem crossing quantum yield (¿ISC = 0.8), (ii) a triplet excited state energy of ca. 67 kcal mol¿1, and (iii) a quantum yield of singlet oxygen formation (¿¿) of 0.3. Furthermore, laser flash photolysis studies revealed a triplet¿triplet energy transfer from the triplet excited state of ppRSV to thymidine, leading to the formation of cyclobutane thymidine dimers, an important type of DNA lesion. Finally, tryptophan has been used as a probe to investigate the type I and/or type II character of ppRSV-mediated oxidation. In this way, both an electron transfer process giving rise to the tryptophanyl radical and a singlet oxygen mediated oxidation were observed. On the basis of the obtained results, rosuvastatin, through its major photoproduct ppRSV, should be considered as a potential sensitizer., Spanish Government (CTQ2009-13699, RyC-2007-00476, PFIS FI09/00312) is gratefully acknowledged for financial support.

[EN] Three drugs containing the naphthalene (NP) chromophore, namely, naproxen (NPX), propranolol (PPN), and cinacalcet (CIN), but with different affinities toward serum albumins (SAs) and alpha-1-acid glycoproteins (AAGs) have been employed for the assessment of drug distribution in binary SA/AAG systems. These three drugs represent an appropriate choice for checking whether a methodology based on transient absorption spectroscopy of a given reporter can be employed for discrimination between different distribution patterns in multicompartmental biological media. Thus, upon laser flash photolysis (LFP) of NPX, PPN, and CIN in the presence or absence of proteins, the NP triplet excited state ((NP)-N-3*) at similar to 420 nm was always detected, although the kinetics of the decay traces was structure- and medium-dependent. In aerated PBS, only a very short triplet lifetime (tau(T)) was found (1-2 mu s). By contrast, in the presence of SAs, two longer triplet lifetimes (5-76 mu s) were observed, ascribed to (NP)-N-3* within site land site II. Upon binding to AAGs, only a long tau(T) (15-47 mu s) was found. When the two proteins were present simultaneously in the same media, fitting of the decay traces was clearly consistent with a distribution of the drug between the different biological compartments and the bulk solution, which correlates well with the known protein affinities of every drug. Experiments were performed in both human (HSA/HAAG) and bovine protein media (BSA/BAAG). The results showed that SAs are the major carriers for NPX; by contrast, PPN binds preferentially to AAGs. An intermediate situation was found for CIN, which presents comparable affinity for both proteins. The results obtained for the two enantiomers of each drug were very similar, although a small stereodifferentiation was observed between the triplet lifetimes in the protein binding sites., Financial support from the MICINN (Grants CTQ2007-67010 and CTQ2010-14882), from the Generalitat Valenciana (Prometeo Program, Ref 2008/090), from Fundacion Cajamurcia, and from Carlos III Institute of Health (Grant RIRAAF, RETICS program) is gratefully acknowledged.

Cinacalcet (CIN) is a calcimimetic drug, which contains a naphthalene chromophore and binds almost quantitatively to human serum albumin (HSA). In the present work, the excited states of CIN have been characterized in order to obtain relevant information about complexation of CIN with HSA. The fluorescence spectrum in acetonitrile, at lambda(exc) = 290 nm, displayed two bands with maxima at 332 and 439 nm, assigned to the monomer and exciplex emission. Upon protonation of the amino group, the exciplex band disappeared, with a concomitant increase of the monomer emission intensity. Time-resolved fluorescence evidenced an intramolecular dynamic quenching, attributed to exciplex formation and/or photoinduced electron transfer, in agreement with the favorable thermodynamics predicted by the Rehm-Weller equations. Diffusion controlled dynamic quenching of CINH(+) fluorescence by oxygen was observed. The emission properties in PBS were similar to those obtained for CINH(+) in acetonitrile. Laser flash photolysis (LFP) of CIN and CINH(+) in aCetonitrile/N(2), at lambda(exc) = 308 nm, gave rise to the naphthalene-like triplet excited states, with maxima at 420 nm and lifetimes of 4 and 7 mu s; they were efficiently quenched by oxygen. No significant singlet excited state interaction was observed in CINH(+)/HSA complexes, as revealed by the emission spectra, which were roughly explained taking into account the relative contributions of drug and protein in the absorption spectra. Upon LFP of the complexes, triplet excited states were generated; the decays monitored at 420 nm were satisfactorily fitted using a function containing two monoexponential terms, corresponding to a Short-lived (tau(1) = 8 mu s) and a long-lived (tau(2) = 37 mu s) component. This indicates that the drug is incorporated into two different binding sites of HSA. Despite the long triplet lifetimes of the CINH(+)/HSA complexes, the rate constant of quenching by oxygen was found to be 2 orders of magnitude lower than that determined in acetonitrile, which can be attributed to the relative slower diffusion rates in this microheterogeneous system. Therefore, the protein microenvironment protects cinacalcet from attack by oxygen; this prevents the phototoxic effects caused by formation of singlet oxygen and results in an enhanced photosafety of the drug., Financial support from the MICINN (Grant CTQ2007-67010), from the Generalitat Valenciana (Prometeo Program, ref 2008/090) and from Carlos III Institute of Health (Grant RIRAAF, RETICS program) is gratefully acknowledged.

[EN] : In the present work, the in¿uence of serum albumins as biological hosts on the well-established photo-Fries rearrangement has been investigated. For this purpose, 4-methoxy-1-naphthyl hydrogen succinate and glutarate (1a,b) as well as the corresponding acetate (1c), have been selected as substrates. Special attention has been devoted to the e¿ect of the binding site location and serum albumin species on the outcome of the reaction. In a ¿rst stage, the stabilizing e¿ect of the biomacromolecule on the intramolecularly catalyzed hydrolysis of succinate 1a was observed. Then, 1b and 1c were considered for their interaction with proteins in site II and site I, respectively. Site assignment was con¿rmed by ¿uorescence displacement experiments with dansylamide and dansylglycine. More- over, spectroscopic analysis showed a site dependent quantum yield of product formation for human and bovine serum albumin., Spanish Government (CTQ2009-13699 project, Ramon y Cajal contract to V.L.-V. and JAE predoc contract to MM.), Generalitat Valenciana (Prometeo Program 2008/090 and GV/2009/051 projects) and Universidad Politecnica de Valencia (PAID 06-08 project) are gratefully acknowledged for financial support.

[EN] Encapsulation within transport proteins strongly reduces the photooxidation rate of (S)- and (R)-2-(9-anthracenyl)propanoic acid (1) and results in a significant stereodifferentiation. The most remarkable effects are observed within human serum albumin (HSA)., Financial support from the MICINN (Grant CTQ2010-14882), the Generalitat Valenciana (Prometeo Program, ref 2008/090), and the Carlos III Institute of Health (Red RETICS) is gratefully acknowledged. We also thank Dr. A. Llamas-Saiz and Servicio de Raios X from Universidad de Santiago for his advice and skillfull technical assistance. Dedicated to the memory of Prof. Rafael Suau.

[EN] In the present work, a systematic study on hydrogen abstraction by the excited triplet states of 4-methoxybenzophenone (1) and 4,40-dimethoxybenzophenone (2) from 1,4-cyclohexadiene (3), 4-methylphenol (4), 1,2,3,4-tetrahydroquinoline (5), and 1-methyl-1,2,3,4-tetrahydroquinoline (6) in different media has been undertaken. Laser flash photolysis (LFP) revealed that in nonpolar solvents, 1 and 2 triplets have a n¿* configuration with the typical benzophenone-like T-T absorption spectrum (¿max ca. 525 nm). Conversely, in aqueous solution, transient absorption spectra with maxima at 450 and 680 nm, attributed to the ¿¿* triplet, were obtained. Quenching of 1 or 2 triplet by 3 led to ketyl radical formation with rate constants in the range of 106 108M 1 s 1, being one order of magnitude higher in acetonitrile than in aqueous media. The rate constants of quenching by 4 and 5 were similar in both polar and nonpolar solvents; the highest value was found for 6 in acetonitrile ((6.3 to 6.9) 109M 1 s 1). For mechanistic insight, LFP of 1 or 2 in the presence of dimethoxybenzene as electron donor was performed. The results showed that in this case, triplet quenching is favored in aqueous solution. In addition, 2 included in human serum albumin (HSA) was submitted to LFP. The decay kinetics, monitored at 430 nm, fitted well with three lifetimes of 0.45, 1.4, and 14.4 ¿s assignable to 2 in bulk solution and in site II or in site I of HSA, respectively. This assignment was confirmed by using oleic acid and ibuprofen as selective displacement probes, Financial support from the MICINN (grants: CTQ2010-99010) and the Generalitat Valenciana (Prometeo Program) is gratefully acknowledged.

[EN] Hydrogen abstraction from the C-7 position of cholesterol (Ch) by triplet excited benzophenone (BZP) exhibits remarkable solvent-dependence in product studies. Kinetic measurements on the intramolecular version of the process in dyads containing covalently linked Ch and BZP units reveal important solvent effects and significant stereodifferentiation., Financial support from the MICINN (Grants CTQ2009-13699 and CTQ2010-19909), from the Generalitat Valenciana (GV/2009/104) and from Carlos III Institute of Health (Grant RIRAAF, RETICS program) is gratefully acknowledged. Dedicated to Prof. Dr. Carmen Najera on the occasion of her 60th birthday.

The mechanistic aspects of the radical cationic version of the [4 + 2] cycloaddition between thiobenzophenone 1 and three aryl-substituted alkenes 2a-c have been studied using DFT methods at the UB3LYP/6-31G level of theory. In the ground state, the Diels-Alder reaction follows an asynchronous concerted mechanism; the large activation energy associated with bond formation prevents this process. After generation of the radical cation (RC), formation of a molecular complex (MC) between 1 and 2a-c initiates a stepwise mechanism, with attack of the sulfur atom of 1 to the aryl-conjugated position of 2a-c. Subsequent ring closure is the rate-determining step of these cycloadditions. Methoxy or dimethylamino substitution at the aryl group, while stabilizing the corresponding RC, results in a less exothermic formation of MC and a significant increase of the cycloaddition barrier. Fil: Heredia, Luis Domingo. Universidad de Valencia; España Fil: Pérez-Ruiz, Raul. Universidad Politécnica de Valencia; España Fil: Argüello, Juan Elias. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; Argentina Fil: Miranda, Hernán Miguel. Universidad Politécnica de Valencia; España

[EN] Laser flash photolysis (LFP) has been used to determine the degree of binding of (S)- or (R)-flurbiprofen methyl ester (FBPMe) to human and bovine serum albumins (HSA and BSA, respectively). Regression analysis of the triplet decay of the drug (lambda = 360 nm) in the presence of the proteins led to a satisfactory fitting when considering a set of three lifetimes; the corresponding A(free), A(I) and A(II) preexponential coefficients can be correlated with the presence of FBPMe in the bulk solution and within the two known binding sites. The most remarkable differences between HSA and BSA were found under nonsaturating conditions; thus, when the [FBPMe]/[SA] ratio was 1: 1, all the drug was bound to HSA, whereas 20-30% of it remained free in the bulk solution in the presence of BSA. The UP approach was also applicable to the study of more complex FBPMe/HSA/BSA mixtures; the obtained results were in good agreement with the previous findings in FBPMe/HSA and FBPMe/BSA systems. This suggests the possibility of making use of the transient triplet-triplet absorption for investigating the distribution of a drug between several compartments in different host biomolecules., Financial support from the MCYT (CTQ2004-03811 and CTQ2007-67010) and the Generalitat Valenciana (GV06/099) is gratefully acknowledged. I.V. thanks MEC for a fellowship.

[EN] Fluorescence and laser-flash photolysis measurements have been performed on two pairs of diastereomeric dyads that contain the nonsteroidal anti-inflammatory drug (S)- or (R)-flurbiprofen (FBP) and (S)-tryptophan (Trp), which is a relevant amino acid present in site I of human serum albumin. The fluorescence spectra were obtained when subjected to excitation at 266 nm, where similar to 60% of the light is absorbed by FBP and similar to 40% is absorbed by Trp; the most remarkable feature observed in all dyads was a dramatic fluorescence quenching, and the residual emission was assigned to the Trp chromophore. In addition, an exciplex emission was observed as a broad band between 380 and 500 nm, especially in the case of the (R,S) diastereomers. The fluorescence lifetimes (tau(F)) at lambda(em) = 340 nm were clearly shorter in the dyads than in Trp-derived model compounds; in contrast, the values of tau(F) at lambda(em) = 440 nm (exciplex) were much longer. On the other hand, the typical FBP triplet-triplet transient absorption spectrum was obtained when subjected to laser-flash photolysis, although the signals were less intense than when FBP was directly excited under the same conditions. The main photophysical events in FBP-Trp dyads can be summarized as follows: (1) most of the energy provided by the incident radiation at 266 nm reaches the excited singlet state of Trp ((1)Trp*), either via direct absorption by this chromophore or by singlet singlet energy transfer from excited FBP ((FBP)-F-1*); (2) a minor, yet stereoselective deactivation of (FBP)-F-1* leads to detectable exciplexes and/or radical ion pairs; (3) the main process observed is intramolecular (1)Trp* quenching; and (4) the first triplet excited-state of FBP can be populated by triplet-triplet energy transfer from excited Trp or by back-electron transfer within the charge-separated states., Financial support from the MCYT (CTQ2004-03811) and the Generalitat Valenciana (GV06/099) is gratefully acknowledged. Author I.V. thanks MEC for a fellowship.

Organic extracts from mycelium and culture broth of 21 Penicillium isolates have been tested for insecticidal, insect anti-juvenile hormone (anti-JH), and antifungal activities. Culture broth extracts were the most active, mainly against insects; nearly 25% of them have shown high entomotoxicity (100% mortality at 100 μg/cm2). A strong in vivo anti-JH activity against Oncopeltus fasciatus Dallas was detected in the culture broth extracts from P. brevicompactum P79 and P88 isolates. The two new natural products isolated from P79, N-(2-methyl-3-oxodec-8-enoyl)-2-pyrroline (1) and 2-hept-5-enyl-3-methyl-4-oxo-6,7,8,8a-tetrahydro-4H-pyrrolo[2,1-b]-1,3-oxazine (2), possessed anti-JH and insecticidal activity, respectively, against O. fasciatus. Synthesized natural compound 1 has shown an ED50 of 0.7 μg/nymph when assayed on newly molted fourth-instar nymphs of O. fasciatus. Promising biological activities have also been detected in the synthetic precursors. Keywords: Penicillium; insecticide; fungicide; anti-J...

Chiral recognition is a subject of increasing interest in photochemistry.1 In principle, this can be achieved with optically active photosensitizers if an enantiodifferentiating interaction occurs in the relevant excited state. Photosensitized electron transfer processes appear specially suitable for such purposes, as the donor and the acceptor must form a highly coupled system for some time.2 The use of chiral compounds as both excited sensitizers and quenchers could enable examination of pure chiral discrimination through comparison of the quenching rates, since enantiomers have otherwise the same electronic nature and the same size. Leigh et al.3 have suggested that hydrogen abstraction from phenols by carbonyl π,π* triplets involves electron transfer within a hydrogen-bonded triplet exciplex, followed by proton transfer. In this context, we have prepared bichromophoric compounds containing enantiomerically pure aryl ketones and phenols, to check the stereochemical aspects of intramolecular electron transfer by means of laser flash photolysis studies. Benzoylthiophene is a heterocyclic diaryl ketone with a lowest lying π,π* triplet.4 This excited state involves predominantly the thenoyl chromophore; it has an energy4 of ca. 63 kcal mol-1 and is able to react with phenols, such as p-cresol and tyrosine methyl ester.5 Both substructures are present in the four enantiomerically pure bichromophoric compounds prepared in this work: TPATyr [(R,S)-1, (S,S)-1] and SUP-Tyr [(R,S)-2, (S,S)-2] (Scheme 1). We have studied the intramolecular electron-transfer process by laser flash photolysis through phenol quenching of the ketone triplet state and found a high degree of stereoselectivity, which agrees with a geometry where interaction between the π-systems of the phenol and the aromatic ketone is maximized. Compounds 1 and 2 differ in the relative aromatic ketone versus phenol orientation. They were obtained by condensation of the corresponding racemic acid, tiaprofenic acid (TPA) or suprofen (SUP), with the methyl ester of the natural occurring amino acid (S)-tyrosine, in the presence of a carbodiimide {(1-ethyl-3-[3dimethylamino]propylcarbodiimide), EDC}. In both cases, after purification of the resulting amides, one of the diastereoisomers crystallized. The other stereoisomers were further purified by HPLC chromatography [potassium dihydrogen phosphate (0.06 M):acetonitrile:triethylamine (317:183:0.1 by volume)]. All the bichromophoric compounds were fully characterized by 1H NMR, 13C NMR, and elemental analysis.

[EN] A new natural product with in vivo anti-juvenile hormone (JK) activity, N-(2-methyl-3-oxodecanoyl)-2-pyrroline (2), has been isolated from Penicillium brevicompactum Dierckx. Its structure has been tentatively assigned based on spectral data and unambiguously confirmed by alternative syntheses. Compound 2 has been prepared by means of a sequence of reactions beginning with acylation of Meldrum's acid by octanoyl chloride. The subsequent steps have been aminolysis of the resultant intermediate with pyrrolidine,;alkylation of the active position with iodomethane, introduction of a methoxy group in the pyrrolidine ring by anodic oxidation, and final elimination of methanol through adsorption on SiO2 and heating. The natural product 2 and its bicyclic isomer 2-heptyl-3-methyl-4-oxo-6,7,8,8a-tetrahydro-4H-pyrrolo [2,1-b]-1,3-oxazine (3) are also obtained. This reveals that 2 can be biogenetically related to the recently discovered brevioxime (1). Compound 2 and the synthetic precursors of 2 have shown important biological activities as insecticides (against Oncopeltus fasciatus Dallas) and fungicides. The natural product induces precocious metamorphosis in the target insect (70% precocious adults at 10 mu g/nymph). In view of the above results, these products could be useful as lead molecules for the synthesis of analogues with enhanced biological activities., The authors acknowledge the financial support of the Institucio´ Valenciana d’Estudis i Investigacio´ (fellowship to A.C.), Comisión Interministerial de Ciencia y Tecnología (CICYT), and Consejeria de Agricultura P. y A. de la C. Valenciana.