Kilo-Scale GMP Synthesis of Renewable Semisynthetic Vaccine-Grade Squalene.

Emulsions of the triterpene squalene ((6E,10E,14E,18E)-2,6,10,15,19,23-hexamethyltetracosa-2,6,10,14,18,22-hexaene, CAS 111-02-4) have been used as adjuvants in influenza vaccines since the 1990s. Traditionally sourced from shark liver oil, the overfishing of sharks and concomitant reduction in the oceanic shark population raises sustainability issues for vaccine adjuvant grade squalene. We report a semisynthetic route to squalene meeting current pharmacopeial specifications for use in vaccines that leverages the ready availability of trans-ß-farnesene ((6E)-7,11-dimethyl-3-methylene-1,6,10-dodecatriene, CAS 18794-84-8), manufactured from sustainable sugarcane via a yeast fermentation process. The scalability of the proposed route was verified by a kilo-scale GMP synthesis. We also report data demonstrating the synthesized semi-synthetic squalene's physical stability and biological activity when used in a vaccine adjuvant formulation.

Cycloalkane and alicyclic heterocycle complexation by new switchable resorcin[4]arene-based container molecules: NMR and ITC binding studies.

The synthesis and structural characterization of novel, "molecular basket"-type bridged cavitands is reported. The resorcin[4]arene-based container molecules feature well-defined cavities that bind a wide variety of cycloalkanes and alicyclic heterocycles. Association constants (K(a)) of the 1:1 inclusion complexes were determined by both (1)H NMR and isothermal titration calorimetry (ITC). The obtained K(a) values in mesitylene ranged from 1.7×10(2) M(-1) for cycloheptane up to 1.7×10(7) M(-1) for morpholine. Host-guest complexation by the molecular baskets is generally driven by dispersion interactions, C-H···π interactions of the guests with the aromatic walls of the cavity, and optimal cavity filling. Correlations between NMR-based structural data and binding affinities support that the complexed heterocyclic guests undergo additional polar C-O···C=O, N-H···π, and S···π interactions. The first crystal structure of a cavitand-based molecular basket is reported, providing precise information on the geometry and volume of the inner cavity in the solid state. Molecular dynamic (MD) simulations provided information on the size and conformational preorganization of the cavity in the presence of encapsulated guests. The strongest binding of heterocyclic guests, engaging in polar interactions with the host, was observed at a cavity filling volume of 63 ± 9%.

Syntheses and properties of 1,6 and 1,7 perylene diimides and tetracarboxylic dianhydrides.

Via Sonogashira cross-coupling with different alkynes, 1,6 and 1,7 perylene diimides (PDIs) and perylene tetracarboxylic dianhydrides (PTCDs) were synthesized from the corresponding regioisomeric mixture of 1,6/1,7-dibromo precursors. Both bulky triphenyl propyne (TPP) groups and nonbulky hexyl groups allow for facile chromatographic separation. The optical properties of these compounds are discussed. Neutral bay substituents hypsochromically shift both the absorption and emission through deformation from planarity of the perylene core.

Two-photon absorption properties of two-dimensional π-conjugated chromophores: combined experimental and theoretical study.

The two-photon absorption (TPA) properties of four TPEB [tetrakis(phenylethynyl)benzene] derivatives (TD, para, ortho, and meta) with different donor/acceptor substitution patterns have been investigated experimentally by the femtosecond open-aperture Z-scan method and theoretically by the time-dependent density-functional theory (TDDFT) method. The four compounds show relatively large TPA cross sections, and the all-donor substituted species (TD) displays the largest TPA cross-section σ(2) = 520 ± 30 GM. On the basis of the calculated electronic structure, TD shows no TPA band in the lower energy region of the spectrum because the transition density is concentrated on particular transitions due to the high symmetry of the molecular structure. The centrosymmetric donor-acceptor TPEB para shows excitations resulting from transitions centered on D-π-D and A-π-A moieties, as well as transition between the D-π-D and A-π-A moieties; this accounts for the broad nature of the TPA bands for this compound. Calculations for two noncentrosymmetric TPEBs (ortho and meta) reveal that the diminished TPA intensities of higher-energy bands result from destructive interference between the dipolar and three-state terms. The molecular orbitals (MOs) of the TPEBs are derivable with linear combinations of the MOs of the two crossing BPEB [bis(phenylethynyl)benzene] derivatives. Overall, the characteristics of the experimental spectra are well-described based on the theoretical analysis.

Computational analysis on the dual reactivity of conjugated "ene-ene-yne" systems.

The design of new reactions that yield benzo-fused five- or six-membered rings arising from conjugated ene-ene-yne precursors was examined computationally. Inclusion of heteroatoms (particularly N) in the bond making position was shown to lower activation energies due to participation of the lone pair electrons in the cyclization reactions. By systematically varying the atomic configuration in the ene-ene-yne system, the influence of heteroatoms was used to identify optimal candidates for future experimental study.

Reactions in the conjugated 'ene-ene-yne' manifold: five-membered ring fragmentation and ring formation via coarctate/pseudocoarctate mechanisms.

The fragmentation of a 5-membered heteroaromatic ring to afford a conjugated ene-ene-yne skeleton, and the corresponding reverse process, cyclization of the hetero-ene-ene-yne motif to generate a variety of heterocyclic systems, are the subject of this review. These synthetically useful reactions, which proceed through a coarctate/pseudocoarctate mechanistic pathway, are unique in that they involve the generation of either a carbene or nitrene intermediate, and provide access to hard to obtain heterocyclic or ene-ene-yne structures. While fragmentation of heteroaromatic rings containing a exocyclic carbene or nitrene has been well documented in the literature for over 40 years, the use of hetero-ene-ene-yne precursors to synthesize heterocycles is a relatively new approach that is generating much interest in the literature. This review highlights both the synthetic and mechanistic aspects of these unique reactions.

CuCl-induced formation and migration of isoindazolyl carbenoids.

Two azo-ene-butadiyne conjugated systems undergo CuCl-mediated cyclization to afford isoindazolyl carbenoids that could be trapped with 2,3-dimethyl-2-butene as [2+1] cycloaddition products. X-ray structure analysis of the resultant cyclopropanes showed that formal migration to the distal carbenoid isomer and subsequent trapping had occurred. The possible CuCl-induced cyclization/migration pathways were explored using density functional theory, which indicated that the reaction most likely occurred via coordination of CuCl to the distal alkyne bond.

Systematic structure-property investigations and ion-sensing studies of pyridine-derivatized donor/acceptor tetrakis(arylethynyl)benzenes.

Nine structural isomers of a tetrakis(arylethynyl)benzene chromophore functionalized with dibutylaniline and pyridine units as respective donors and acceptors have been synthesized and their steady-state spectroscopic parameters investigated. The effects of small structural variations on the electronic absorption and emission spectra have been explored in evaluation of their potential as optical materials components. These structural variations have predictable consequences and thus allow fine-tuning of the optoelectronic properties for specialized applications. Strong solvatochromism is also displayed. Their response to protonation and metal ion complexation caused dynamic shifts in the emission spectra, providing evidence for a stepwise intramolecular charge-transfer switching phenomenon manifested by either hypsochromic or bathochromic shifts in the fluorescence lambda max. These shifts are believed to correlate strongly to the relative energies of the fluorophore's HOMO and LUMO levels. The complete array of compounds represents an interesting set of candidates for fluorescent sensing device components.

Synthesis of 2H-indazoles via Lewis acid promoted cyclization of 2-(phenylazo)benzonitriles.

Lewis-acid promoted "coarctate" cyclization of 10 2-(phenylazo)benzonitrile derivatives furnishes the isoindazole ring system in ca. 65-95% yield. A plausible mechanism for this unusual transformation is proposed.

Biscyclization reactions in butadiyne- and ethyne-linked triazenes and diazenes: concerted versus stepwise coarctate cyclizations.

A series of alkyne-linked bis-2H-indazoles has been prepared by the double cyclization of ethyne- or butadiyne-linked phenyltriazene or phenyldiazene moieties. Even though there are two five-membered ring cyclizations and several triple bond shifts involved, the reactions proceed rapidly under neutral conditions with mild heating, affording the heterocycles in excellent yields. DFT calculations, in agreement with experimental observations, indicate that the reactions: (1) occur via a very short-lived carbene intermediate, (2) are concerted via an asymmetrical transition state, or (3) are even synchronous, with as many as 16 bonds that are made or broken simultaneously. The biscyclizations presented herein strikingly illustrate the concept of coarctate reactions, the stabilization of transition states by coarctate Möbius aromaticity, the ethynologation principle, and the stereochemical rules.

Structure-property relationships of donor/acceptor-functionalized tetrakis(phenylethynyl)benzenes and bis(dehydrobenzoannuleno)benzenes.

A series of tetrakis(phenylethynyl)benzenes and bis(dehydrobenzoannuleno)benzenes have been synthesized containing tetra-substitutions of neutral, donor, and mixed donor/acceptor groups. To ascertain the importance of substitutional and structural differences of the phenylacetylenes, the optical absorption and emission properties of each series were examined. Conjugation effectiveness, electron density, planarity, and geometry of charge-transfer pathways were found to have a pronounced effect on the overall optical and material properties. Considerable self-association behavior due to face-to-face stacking in solution was observed for donor/acceptor-functionalized macrocycles and was quantified by concentration-dependent (1)H NMR measurements. A solvent-dependent polymerization of one macrocycle regioisomer was observed and characterized. To provide further insight into the energy levels and electronic transitions present, computational studies of each system were performed.

Experimental and theoretical investigation of the coarctate cyclization of (2-Ethynylphenyl)phenyldiazenes.

A new route to substituted 2-phenyl-2H-indazoles through the cyclization of (2-ethynylphenyl)phenyldiazenes is presented. A coarctate reaction pathway forms the isoindazole carbene under neutral conditions, at moderate temperatures, and without the requirement of a carbene stabilizer. A wide variety of previously unknown diazene precursors was synthesized and cyclized. Trapping of the carbene with a silyl alcohol followed by deprotection affords the 3-hydroxymethyl-2-phenyl-2H-indazoles in good overall yield. The free carbene could also be trapped as a [2 + 1] cycloadduct with 2,3-dimethyl-2-butene.