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Herein we examine the determinants of the allosteric inhibition of the mitochondrial chaperone TRAP1 by a small molecule ligand. The knowledge generated is harnessed into the design of novel derivatives with interesting biological properties. TRAP1 is a member of the Hsp90 family of proteins, which work through sequential steps of ATP processing coupled to client-protein remodeling. Isoform selective inhibition of TRAP1 can provide novel information on the biomolecular mechanisms of molecular chaperones, as well as new insights into the development of small molecules with therapeutic potential. Our analysis of the interactions between an active first-generation allosteric ligand and TRAP1 shows how the small molecule induces long-range perturbations that influence the attainment of reactive poses in the active site. At the same time, the dynamic adaptation of the allosteric binding pocket to the presence of the first-generation compound sets the stage for the design of a set of second-generation ligands: the characterization of the formation/disappearance of pockets around the allosteric site that is used to guide optimize the ligands' fit for the allosteric site and improve inhibitory activities. The effects of the newly designed molecules are validated experimentally in vitro and in vivo. We discuss the implications of our approach as a promising strategy towards understanding the molecular determinants of allosteric regulation in chemical and molecular biology, and towards speeding up the design of allosteric small molecule modulators.

Intelligent packaging represents an emerging trend in the food industry, especially for highly perishable foods like milk and dairy products. Despite the apparent simplicity, miniaturized BCP-EVOH@ sensor, made of bromocresol purple (BCP) covalently bound to ethylene-vinyl alcohol (EVOH) copolymer, meets the goal of milk freshness monitoring during chilled storage, allowing both naked-eye evaluation and chemometric-assisted spoilage modelling and measurements.

Nitrosocarbonyl intermediates on solid polystyrenic support are generated at room temperature by the mild oxidation of resin-bound stable nitrile oxides. They undergo one-pot ene reactions with tetramethyl- and trimethyl-ethylene and other highly substituted olefins. Less substituted ethylenes as well as cyclohexene and cyclopentene are heavily disfavoured and nitrosocarbonyls on solid phase undergo fast dimerization and/or decomposition pathways. These outcome strongly limit the SP applications in organic synthesis, although applicable to structurally specific N-alkenyl hydroxamic acids.

The facial selectivity in the nitrile oxide cycloaddition reactions of 4-hydroxy-2-cyclopentenone and its bulky t- butyloxy derivative is reported. A quantitative evaluation of the solvent effect on the hydrogen bonding directing ability is given, showing the presence of some syn -stereoselectivity even in good H-bond acceptor solvents. The stereoselectivities of the O - t- butyl derivative may serve as reference data for more complex systems and point to the existence of a sole steric effect on the directivity; M(II) ions did not significantly improve the selectivity. The results are also discussed in light of the potential application of these scaffolds in the nucleoside analogue synthesis.

A quantitative evaluation of the H-bond directing effect on the stereoselectivity in the cycloaddition of nitrile oxides to 2-cyclopenten-1-ol and allylic cyclopentenyl amides is reported. In apolar solvents the H-bond directing effect promotes a high syn stereoselectivity while H-bond acceptor solvents divert the reactions to the anti face of the dipolarophile. Taft's β parameter gives a good description of the solvent effect on the H-bond directing effect. The persistence of some syn stereoselectivity even in good H-bond acceptor solvents points out the existence of some residual hydrogen bond direction. The syn stereoselectivity in the presence of M(II) salts was also investigated and the results discussed in the light of the potential application of these scaffolds in nucleoside synthesis.

In this paper we report the synthesis, the crystal structure and the optical response of APbX3 (A=MA, DMA, and TMA; X=I, Br) hybrid organic-inorganic materials including some new phases. We observe that as the cation group increases in size, the optical absorption edge shifts to higher energies with energy steps which are systematic and independent on the anion. A linear correlation between the optical bad gap and the tolerance factor has been shown for the series of samples investigated.

Isoxazolino-carbocyclic anthracene nor-nucleosides were prepared through nitrosocarbonyl chemistry and tested for their inhibitory activity against some viruses, such as Herpes simplex viruses of type 1 and 2, Zoster virus and Hepatitis B and C. The activities were almost negligible in most of the cases. A remarkable antiviral activity was found for a specific regioisomer with no cellular toxicity at 1–100 μM dose concentration in the case of Human Papilloma virus.

A variety of symmetric and asymmetric 3,5-heterocyclic disubstituted 1,2,4-oxadiazole-4-oxides have been prepared through cycloaddition of aromatic and heteroaromatic nitrile oxides to heteroaromatic amidoximes. A library of novel, fully characterized, 1,2,4-oxadiazole-4-oxides has been obtained as valuable precursors, upon photochemical activation, of new nitrosocarbonyl intermediates. The photochemical cycloreversion of the 1,2,4-oxadiazole-4-oxides was investigated from the computational point of view and the hydrolysis of the generated nitrosocarbonyl intermediates in water constituted the way for an easy-made HNO generation process because of the photochemical behavior of the parent compounds.

The synthesis of isoxazolino-carbocyclic nor-nucleosides incorporating an anthracene moiety was properly tuned through nitrosocarbonyl intermediates chemistry, and a variety of analogues were attained starting from stereodefined heterocyclic aminols through the linear construction of purine heterocyclic rings. The synthesis hinges on the exo selective 1,3-dipolar cycloaddition of the stable anthracenenitrile oxide to the N-benzoyl-2,3-oxazanorborn-5-ene and simple elaborations of the cycloadducts. A selection of nucleoside derivatives were initially tested for their inhibitory activity against a variety of viruses, including Hepatitis B and C, Human Papilloma virus as well as Influenza viruses of type A and B. Modest anti-viral activities were observed in Hepatitis assays while the activities in the cases of Influenza viruses were almost negligible. Good anti-viral activity was found for compound 11bC with no cellular toxicity at the dose tested in the case of Human Papilloma virus.

The regioisomeric cycloadducts of the bromonitrile oxide to the N-benzoyl-2,3-oxazanorborn-5-ene were easily prepared and elaborated into a novel class of uracil nor-nucleoside derivatives. In the key-synthetic step represented by the reductive N–O bond cleavage, an unusual double ring opening afforded the aminol intermediates containing a β-hydroxynitrile structure. By adapting known protocols, the aminols entered the linear construction of uracil rings. These novel nucleosides were found structurally similar to a potent antiviral compound, Brivudin, and molecular modeling and docking allowed to select one of the two regioisomeric structures as promising candidate for antiviral tests, due to the nice level of binding with the Thymidine Kinase, the enzyme involved in virus replication.

A rapid access to peptidomimetic conformationally constrained γ-amino acids has been developed through the efficient RuO4-mediated oxidation of regioisomeric isoxazolino-2-azanorbornane derivatives. The key intermediates are tricyclic lactams, which are quantitatively hydrolyzed into the desired amino acids. The conformational analysis, conducted by means of DFT calculations, supports the use of these γ-amino acids as β-turn inducers in peptide synthesis.

A new approach to useful precursors for the synthesis of isoxazoline-carbocyclic nucleosides is detailed, starting from the readily available N-benzoyl-2,3-oxazanorborn-5-ene and introducing more polar and hydrophilic functionalities through 1,3-dipolar cycloaddition of carbethoxyformonitrile oxide, generated either from the corresponding hydroximoyl chloride or, more conveniently, by catalyzed condensation with ethyl nitroacetate.

N -Benzoyl-2-oxa-3-azabicyclo[2.2.2]oct-5-ene undergoes cycloaddition with benzonitrile oxide affording a mixture of syn and anti regioisomeric cycloadducts. The anti cycloadducts were easily elaborated to stereodefined isoxazoline-carbocyclic aminols that served as synthons for the linear construction of pyrimidine nucleosides, while the syn cycloadducts do not enter the same synthetic route.

A rapid access to carbocyclic nucleosides containing a fused isoxazoline ring is proposed through the Grieco cycloaddition of cyclopentadiene to iminium salts. The prolific elaboration of the isoxazoline cycloadducts allowed preparation of the target aminols through the unmasking of the hydroxymethylene group at the C3 level of the azanorbornene structure. The heterocyclic aminols are readily converted into nucleosides via the linear construction of purine heterocycles.

A novel approach to useful aminols for the synthesis of carbocyclic nucleosides is reported starting from a convenient source, the 2-azanorborn-5-enes. These are readily available through the Grieco cycloaddition of cyclopentadiene with iminium salts and are reactive dipolarophiles toward nitrile oxides. The prolific elaboration of the isoxazoline cycloadducts allowed preparation of the target aminols through the unmasking of the hydroxymethylene group at the C3 level of the azanorbornene structure.

The molecular and crystal structures of 3,8-diphenyl-3a,4,5,5a,8a,8b-hexahydro-benzo[1,2-d: 3,4-d′]diisoxazole have been XRD determined. The compound crystallizes in the monoclinic system (space group P 2 1 / c ) with cell dimensions a =15.278(1), b =9.839(1), c =10.912(2) A, β =92.15(1)°. The structure was solved from 2193 reflections with I ≥2 σ ( I ). The final R was 0.039 for 289 variables. DFT calculations at the B3LYP/6-31G* level afforded a twist-boat conformer almost identical with the X-ray structure as well as a less stable half-chair conformer which lies 9.7 kJ/mole higher in enthalpy. The near planarity of the two fused isoxazoline rings destabilizes the staggered cyclohexane chair and forces the cyclohexane ring to adopt uncommon conformations.

The dimerization of butadiene has been explored by using DFT methods at the B3LYP level with the 6-311+G** basis set. A concerted bispericyclic TS for the endo pathway and a concerted pericyclic TS for the exo pathway are the lowest passes for the dimerization and occur at almost the same energy thus accounting for the lack of stereochemical preferences in the dimerization. Diradical paths involving two unswitched transoid butadiene moieties are competing and account for the formation of minor amounts of trans-1,2-divinyl cyclobutane and 1,5-cycloctadiene.

The synthesis of novel soluble polymer-supported optically-active oxazolidinone (Evans’ chiral auxiliary) with different chiral monomer/styrene ratios is described. The polymer was obtained in high yields and then functionalized with trans -crotonic anhydride to give a high loading polymer (2.42 mmol/g). The reactivity was tested in the 1,3-dipolar cycloaddition with diphenylnitrone under catalyzed and uncatalyzed conditions. The cycloadducts could be obtained in high purities and fair yields after reductive cleavage. The stereoselectivity is parallel to that obtained with the model substrate under classical solution conditions.

1,3-Dipolar cycloadditions of supported Evans' chiral auxiliary with nitrile oxides and nitrones in the presence of Mg(II) cation as catalyst were evaluated. The presence of acetonitrile as co-solvent was found to be fundamental for the Lewis acid catalysis on solid-phase. The regio- and stereochemical outcome of nitrile oxide cycloadditions is influenced by nearly stoichiometric quantities of the cation, whilst catalytic amounts of Mg(II) influence both the reactivity and the stereoselectivity of the nitrone cycloadditions. The results obtained support a reaction mechanism involving the coordination of the Mg(II) to the dicarbonyl fragment of the chiral auxiliary.

The regiospecific dimerization of methacrolein takes place through a very asynchronous and symmetrical transition structure, which shows a merging of the 4+2 and 2+4 cycloaddition paths. The geometrical features of the transition structures correspond well to a case of diradical formation. A cage of secondary orbital interactions restricts the flexibility of the diradical transition structure and stabilizes it.

The regiochemistry of the cycloadditions of nitrile oxides to crotonaldehyde and cinnamaldehyde has been determined and is dictated by frontier orbital interactions and secondary orbital interactions as well. In cycloadditions to α,β-unsaturated compounds the directive effect of the frontier orbital interactions can be diverted by steric drifts and secondary orbital interactions.

1,2,4-Oxadiazole-4-oxides undergo clean thermal cleavage in refluxing chlorobenzene or xylene to nitriles and nitrosocarbonyl intermediates, which are either trapped with suitable olefins to afford ene adducts or dimerize and rearrange to anhydrides.

Evans' chiral auxiliary was grafted onto both Merrifield and Wang resins and, after functionalisation, they were used as chiral dipolarophiles in a 1,3-dipolar cycloaddition involving both a nitrile oxide and a nitrone. The cycloadducts were cleaved and analysed by chiral HPLC: the recovered supported chiral oxazolidinone was functionalised and reused in further cycloadditions. The stereochemical results as well as the possibility of recycling the chiral linker supports the applicability of solid-supported chiral auxiliaries.

Nitrile oxides are oxidized by tertiary amine N-oxides in different solvents at room temperature to afford in the presence of dienes nitrosocarbonyl adducts in fair yields. The mild conditions used in oxidizing a variety of nitrile oxides promise a wide application of this method in synthetic processes.

Nitroscarbonyl intermediates are photochemically generated from 1,2,4-oxadiazole-4-oxides and efficiently trapped with enes and dienes.

Nitrosocarbonyl intermediates, generated at r.t. by the mild oxidation of nitrile oxides, undergo clean ene reactions with tetramethyl- and trimethyl-ethylene and with cyclohexene. With less substituted ethylenes the ene pathway is still active but the oxidation step of the nitrile oxides competes with the cycloadditions to the olefins.

The cycloaddition of nitrile oxides to amidoximes is a general method for the sinthesis of 3,5-disubstituted 1,2,4-oxadiazole-4-oxides with the same or different substituents. The yields are only moderate since an equivalent amount of the nitrile oxide is consumed by reaction with the amine released in the fragmentation of the primary cycloadducts and reforms the amidoxime. With excess nitrile oxides the 1,2,4-oxadiazole-4-oxides undergo a disproportionation reaction to yield nitroso carbonyl intermediates and 1,2,4-oxadiazoles.

Cycloaddition of benzonitrile oxide to pyridazine affords an isolable mono-cycloadduct. In cycloadditions to pyrimidine and pyrazine the primary mono-cycloadducts are labile intermediates which undergo further cycloaddition affording isolable bis- and tris-cycloadducts.

Addition of N-methyl morpholine N-oxide (NMO) to a nitrile oxide solution in dichloromethane at room temperature in the presence of a diene affords nitroso carbonyl adducts in fair yields.

Several bis-copper (II) complexes with chiral ligands derived from 2-substituted 2-(salicylideneamino) ethanols have been tested as catalysts of enantioselective Michael reactions. The degree of enantioselection is strongly affected by the architecture of the ligand. The best result (75% e.e.) was obtained for a ligand having a substituent potentially suitable to induce the formation of a bis-tetradentate copper (II) complex with a square pyramidal coordination.

Non-classical (bridging) and classical (Woodward–Hoffmann) secondary orbital interactions as well as a favourable electrostatic interaction are involved in the stabilization of the two lowest transition passes of the acrolein dimerization. The heteroatoms provide anchimeric assistance to the hetero Diels–Alder reaction through a neighbouring-group mechanism.

The copper(II) complex of 1-methylisatin-3- p -chlorophenyl hydrazone (2) reacted with dimethyl acetylenedicarboxylate (DMAD) in accordance to two reaction pathways. Oxidation performed by Cu++ gave 1-methyl-3-carbenindolin-2-one (12), trapped by DMAD to give products 3—5, and p -chlorophenylradical (13), trapped either by DMAD to give 6, or by the free ligand 1 to give 7 or by carbenindolinone and DMAD to give 8. The second pathway involved a [2+2] cycloaddition followed by electrocyclic ring opening and intramolecular cyclization to give 1-methyl-2-indolinone-3-spiro-5'-1'- p -chlorophenyl-3', 4'-dimethoxycarbonyl-2'-pyrazoline (9) whose structure and configuration were demonstrated by an independent synthesis. The mechanism of the reaction is discussed.