From propenolysis to enyne metathesis: tools for expedited assembly of 4a,8a-azaboranaphthalene and extended polycycles with embedded BN

The synthesis of BN-containing molecules, which have an interesting isosteric relationship to their parent all-C cores, has drawn a great deal of attention as an avenue to alter and tune molecular function. Nevertheless, many cores with embedded BN are still hard to synthesize, and thus, further effort is required in this direction. Herein, we present an integrated approach to BN-containing polycycles rooted in an exceptionally clean B-N condensation of amines with a tri-allylborane. Having released propene as the only byproduct, the resulting BN precursors are seamlessly telescoped into BN-containing polycyclic cores via a set of additional methodologies, either developed here ad-hoc or applied for the first time for the synthesis of BN-cycles. As the "sharpening stone" of the process, BN-embedded naphthalene, which has previously only been obtained in low yield, can now be synthesized efficiently through propenolysis, ring-closing metathesis and a new high-yielding aromatization. As a more advanced application, an analogously obtained BN-containing bis-enyne is readily converted to BN-containing non-aromatic tetra-, penta- and hexacyclic structures via ring-closing enyne metathesis, followed by the Diels-Alder cycloaddition. The resulting air-sensitive structures are easily handled by preventive hydration (quaternization) of their B-N bridge; reverting this hydration restores the original Bsp2-Nsp2 structure. In the future, these structures may pave the way to BN-anthracenes and other π-extended BN-arenes.

Cyclic Homo- and Heterohalogen Di-λ3-diarylhalonium Structures

In the context of the ever-growing interest in the cyclic diaryliodonium salts, this work presents synthetic design principles for a new family of structures with two hypervalent halogens in the ring. The smallest bis-phenylene derivative, [(C₆H₄)₂I₂]²⁺, was prepared through oxidative dimerization of a precursor bearing the ortho-disposed iodine and trifluoroborate groups. We also report, for the first time, the formation of cycles containing two different halogen atoms. These present two phenylenes linked by hetero-(I/Br) or -(I/Cl) halogen pairs. This approach was also extended to the cyclic bis-naphthylene derivative [(C₁₀H₆)₂I₂]²⁺. The structures of these bis-halogen(III) rings were further assessed through X-ray analysis. The simplest cyclic phenylene bis-iodine(III) derivative features the interplanar angle of ∼120°, while a smaller angle of ∼103° was found for the analogous naphthylene-based salt. All dications form dimeric pairs through a combination of π-π and C-H/π interactions. As the largest member of the family, a bis-I(III)-macrocycle was also assembled using the quasi-planar xanthene backbone. Its geometry enables the two iodine(III) centers to be bridged intramolecularly by two bidentate triflate anions. In a preliminary manner, the interaction of the phenylene- and naphthalene-based bis-iodine(III) dications with a new family of rigid bidentate bis-pyridine ligands was studied in solution and the solid state, with an X-ray structure showing the chelating donor bonding to just one of the two iodine centers.

Ammonium trifluoroborate-modified poly(β-aminoesters): A case study for PET-guided in vivo pharmacokinetic studies of a non-viral gene delivery system

Nucleic acid-based therapies have become a game-changing player in our way of conceiving pharmacology. Nevertheless, the inherent lability of the phosphodiester bond of the genetic material with respect to the blood nucleases severely hampers its delivery in naked form, therefore making it necessary to use delivery vectors. Among the potential non-viral vectors, polymeric materials such as the poly(β-aminoesters) (PBAEs) stand out as promising gene carriers thanks to their ability to condense nucleic acids in the form of nanometric polyplexes. To keep advancing these systems into their translational preclinical phases, it would be highly valuable to gain accurate insights of their in vivo pharmacokinetic profile. We envisaged that positron emission tomography (PET)-guided imaging could provide us with both, an accurate assessment of the biodistribution of PBAE-derived polyplexes, as well shed light on their clearance process. In this sense, taking advantage of the efficient [¹⁹F]-to-[¹⁸F]‑fluorine isotopic exchange presented by the ammonium trifluoroborate (AMBF₃) group, we have designed and synthesized a new ¹⁸F-PET radiotracer based on the chemical modification of a linear poly(β-aminoester). As proof of concept, the incorporation of the newly developed ¹⁸F-PBAE into a model nanoformulation was shown to be fully compatible with the formation of the polyplexes, their biophysical characterization, and all their in vitro and in vivo functional features. With this tool in hand, we were able to readily obtain key clues about the pharmacokinetic behavior of a series of oligopeptide-modified PBAEs (OM-PBAEs). The observations described in this study allow us to continue supporting these polymers as an outstanding non-viral gene delivery vector for future applications.

PET Imaging of Self-Assembled 18 F-Labelled Pd2 L4 Metallacages for Anticancer Drug Delivery

To advance the design of self-assembled metallosupramolecular architectures as new generation theranostic agents, the synthesis of ¹⁸ F-labelled [Pd₂ L₄ ]⁴⁺ metallacages is reported. Different spectroscopic and bio-analytical methods support the formation of the host-guest cage-cisplatin complex. The biodistribution profiles of one of the cages, alone or encapsulating cisplatin have been studied by PET/CT imaging in healthy mice in vivo, in combination to ICP-MS ex vivo.

Exploring benzylic gem-C(sp3)-boron-silicon and boron-tin centers as a synthetic platform

A stepwise build-up of multi-substituted Csp3 carbon centers is an attractive, conceptually simple, but often synthetically challenging type of disconnection. To this end, this report describes how gem-α,α-dimetalloid-substituted benzylic reagents bearing boron/silicon or boron/tin substituent sets are an excellent stepping stone towards diverse substitution patterns. These gem-dimetalloids were readily accessed, either by known carbenoid insertion into C-B bonds or by the newly developed scalable deprotonation/metallation approach. Highly chemoselective transformations of either the C-Si (or C-Sn) or the C-B bonds in the newly formed gem-Csp3 centers have been achieved through a set of approaches, with a particular focus on exploiting the synthetically versatile polarity reversal in organometalloids by λ3-aryliodanes. Of particular note is the metal-free arylation of the C-Si (or C-Sn) bonds in such gem-dimetalloids via the iodane-guided C-H coupling approach. DFT calculations show that this transfer of the (α-Bpin)benzyl group proceeds via unusual [5,5]-sigmatropic rearrangement and is driven by the high-energy iodine(iii) center. As a complementary tool, the gem-dimetalloid C-B bond is shown to undergo a potent and chemoselective Suzuki-Miyaura arylation with diverse Ar-Cl, thanks to the development of the reactive gem-α,α-silyl/BF3K building blocks.

Boron-Wittig olefination with gem-bis(boryl)alkanes

Boron-Wittig reaction as the condensation of lithium α-bis(boryl)carbanions with carbonyl derivatives on route to substituted borylalkenes.

Iodane-Guided ortho C-H Allylation

A metal-free C-H allylation strategy is described to access diverse functionalized ortho-allyl-iodoarenes. The method employs hypervalent (diacetoxy)iodoarenes and proceeds through the iodane-guided "iodonio-Claisen" allyl transfer. The use of allylsilanes bearing electron-withdrawing functional groups unlocks the functionalization of a broad range of substrates, including electron-neutral and electron-poor rings. The resulting ortho-allylated iodoarenes are versatile building blocks, with examples of downstream transformation including a concise synthesis of the experimental antimitotic core of Dosabulin. DFT calculations shed additional light on the reaction mechanism, with notable aspects including the aromatic character of the transition-state structure for the [3,3] sigmatropic rearrangement, as well as the highly stereoconvergent nature of the trans-product formation.

Transition-metal-free B-B and B-interelement reactions with organic molecules

This review is a guided tour along the activation modes and reactivity of B-B, B-Si, B-N, B-S, B-Se and B-P reagents, in the absence of any transition metal complex. Here are disclosed the general concepts related to the homolytic and heterolytic cleavage of B-B and B-interelement bonds, as well as the generation of new C-B and C-interelement bonds, in a selective way. The greener consequences of these novel routes facilitate the gram scale preparations of target functionalised organic compounds. Intrinsic data about the suggested mechanisms and spectroscopic evidence that supports the innovative theories are provided along the review. Since this is a stimulating area of work that has emerged within the last decade, this overview serves as the basis to understand the new trends and hopefully to generate inspiration for future discoveries in the field.

Opportune gem-Silylborylation of Carbonyl Compounds: A Modular and Stereocontrolled Entry to Tetrasubstituted Olefins

An easy access to highly versatile gem-silylboronate synthons is achieved by means of a new olefination reagent, HC(Bpin)₂ (SiMe₃ ). Subsequent silicon or boron-based selective functionalization allows for the modular and stereocontrolled synthesis of all-carbon tetrasubstituted alkenes. A particular attraction of this approach is the iododesilylation reaction, which becomes a pivotal tool for C-Si functionalization.

Synthesis of a Naphthodiazaborinine and Its Verification by Planarization with Atomic Force Microscopy

Aiming to study new motifs, potentially active as functional materials, we performed the synthesis of a naphthodiazaborinine (the BN isostere of the phenalenyl anion) that is bonded to a hindered di-ortho-substituted aryl system (9-anthracene). We used atomic force microscopy (AFM) and succeeded in both the verification of the original nonplanar structure of the molecule and the planarization of the skeleton by removing H atoms that cause steric hindrance. This study demonstrated that planarization by atomic manipulation is a possible route for extending molecular identification by AFM to nonplanar molecular systems that are difficult to probe with AFM directly.

Correction: Unsymmetrical 1,1-diborated multisubstituted sp(3)-carbons formed via a metal-free concerted-asynchronous mechanism

Correction for 'Unsymmetrical 1,1-diborated multisubstituted sp(3)-carbons formed via a metal-free concerted-asynchronous mechanism' by Ana B. Cuenca et al., Org. Biomol. Chem., 2015, 13, 9659-9664.

Unsymmetrical 1,1-diborated multisubstituted sp(3)-carbons formed via a metal-free concerted-asynchronous mechanism

We have experimentally proved the unsymmetrical 1,1-diboration of diazo compounds, formed in situ from aldehydes and cyclic and non-cyclic ketones, in the absence of any transition metal complex. The heterolytic cleavage of the mixed diboron reagent, Bpin-Bdan, and the formation of two geminal C-Bpin and C-Bdan bonds has been rationalised based on DFT calculations to occur via a concerted-asynchronous mechanism. Diastereoselection is attained on substituted cyclohexanones and DFT studies provide understanding on the origin of the selectivity. The alkoxide-assisted selective deborylation of Bpin from multisubstituted sp(3)-carbon and generation of a Bdan stabilized carbanion, easily conducts a selective protodeboronation sequence.

Mixed diboration of alkenes in a metal-free context

Experimental and theoretical rationalization on regioselective mixed diboration of alkenes, with the unsymmetrical diboron reagent Bpin-Bdan, providing the protecting Bdan moiety in the internal position.

Organocatalytic functionalisation through boron chemistry

Diboron reagents can be activated both, from a metal or free-metal context, and consequently the addition of boryl units to unsaturated substrates proceeds sometimes with complementary selectivity. We highlight here the power of boron chemistry to functionalize molecules and provide new routes towards challenging compounds.

Gold(i)-catalysed cascade reactions in the synthesis of 2,3-fused indole derivatives

Unactivated alkenes and 1,3-unsubstituted indoles in gold(i)-catalysed hydroaminative/arylative cascade cyclizations.

TT genotype of transforming growth factor beta1 +869C/T is associated with the development of chronic kidney disease after liver transplantation

BACKGROUND

Chronic kidney disease (CKD) is a frequent complication in patients with liver transplantation (LT), and calcineurin inhibitor chronic nephrotoxicity, mediated by transforming growth factor beta1 (TGF-β1) is an important contributing factor. The aim of this study was to assess the influence of genetic polymorphisms of TGF-β1 in the development of CKD at 6 months after transplantation.

METHODS

One hundred sixty-four LT patients (63.4% male; overall mean age, 48.7 ± 11.6 years) were included in the analysis. CKD was considered at the 6th month after LT and was defined as an estimated glomerular filtration rate (eGFR) of <60 mL/min/1.73 m(2) as calculated on the basis of Modification of Diet in Renal Disease 4-variable equation. TGF-β1 +869 C/T and +915 G/C polymorphisms were analyzed with the use of hybridization with fluorescent probes and analysis by means of flow cytometry with the Luminex system. The association between the presence of CKD at 6 months and these polymorphisms, as well as with other known risk factors for CKD after LT, was considered.

RESULTS

In the univariate analysis, the TT genotype of TGF-β1 +869 (P = .036; odds ratio, 2.1; 95% confidence interval, 1.1-4.2), age at LT (P < .001), pre-transplantation serum creatinine levels (P = .03), eGFR (P < .001), CKD (P = .027), and immunosuppression with cyclosporine (P = .017) were associated with CKD at 6 months after transplantation. In the multivariate analysis, TGF-β1 +869TT genotype (P = .017), immunosuppression with cyclosporine (P = .002), age at LT (P = .024), and pre-transplantation CKD (P < .001) remained as independent variables associated with the development of CKD at 6 months after transplantation.

CONCLUSIONS

The genetic polymorphism TGF-β1 +869 C/T may be an independent risk factor for CKD after liver transplantation.

CC genotype at rs12979860 of IL28B is associated with lower risk of new-onset diabetes after transplantation in adult patients with liver transplantation for hepatitis C cirrhosis

INTRODUCTION

New-onset diabetes mellitus after transplantation (NODAT) in patients undergoing liver transplantation (LT) for hepatitis C virus (HCV)-related cirrhosis is associated with more aggressive HCV recurrence on the graft, rapid progression of fibrosis, and lower rate of sustained viral response to antiviral therapy. The CC genotype at rs12979860 of the IL28B is associated with greater rates of spontaneous clearance of HCV and response to antiviral therapy. IL28B acts on the interferon-stimulated genes through the JAK-STAT pathway, which is related to the development of insulin resistance. The aim of this study was to investigate whether IL28B rs12979860 polymorphism is associated with the development of NODAT after LT for cirrhosis owing to HCV infection.

METHODS

We analyzed 99 patients (age, 52.7 ± 9.4 years; 70% male) who underwent LT for HCV-related cirrhosis, with ≥1 year of follow-up and with available DNA sample. NODAT was defined starting from the sixth month after LT, according to the international consensus guidelines. Genotyping was carried out by real-time polymerase chain reaction and analysis of the melting temperature with the LightCycler 480 system.

RESULTS

Twenty-eight patients (28.3%) developed NODAT. CC genotype at rs12979860 of IL28B was associated with a lesser incidence of NODAT versus non-CC genotypes (P = .05; odds ratio, 0.31; 95% CI, 0.11-0.92). We did not find any association between NODAT and age at transplantation, gender, pretransplant body mass index, presence of hepatocellular carcinoma, type of initial immunosuppression (cyclosporine, tacrolimus or corticosteroids) or acute rejection treated with steroids.

CONCLUSION

The CC genotype at rs12979860 of IL28B is a protective factor for NODAT in patients with LT for HCV-related cirrhosis.

Water compatible gold(III)-catalysed synthesis of unsymmetrical ethers from alcohols

An efficient and broad-scoped method for the preparation of unsymmetrical ethers from alcohols catalysed by the simplest and least expensive gold catalyst, NaAuCl(4), is described for the first time. The procedure enables the etherification of benzylic and tertiary alcohols with moderate to good yields under mild conditions with low catalyst loading. Symmetrical ethers, the usual side products in the etherification of alcohols, were not detected in this case. The formation of the racemic ether from a chiral benzyl alcohol suggests the intermediacy of a carbocation, which has not previously been postulated for gold-catalysed reactions involving alcohols.