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A series of donor-acceptor p-nitro-p'-alkoxy (OR) substituted (E,E,E)-1,6-diphenyl-1,3,5-hexatrienes were prepared and their properties and crystal structures investigated. The flouresence spectra of these crystals were red-shifted relative to those for the solutions in low polar solvents, which can be attributed to the planarization of molecules in the solid state and to the strong intermolecular interactions in crystals.

The change in polyene bond lengths with distance from the polyacene and the modification of the HOMO-LUMO energy gap brought about by chemisorption of the polyene on some polyacenes is presented. The conclusion states that the dispersion interactions would play a role in the interaction between planar conjugated systems.

A stable class of reagents capable of effecting transformations like halonium-induced polyene cyclizations for a wide range of electron-rich and udeficient terpenes derived from geraniol, farsenol and nerol are described, enabling the synthesis of a diverse array of complex chlorine-, bromine- and iodine-containing polycyclic frameworks. The studies have led to the total synthesis and structural revision of the anti-HIV natural product peyssonol A as well as an efficient and concise inaugural total synthesis of pesyssonoic acid A.

Highly efficient catalytic enantioselective cationic polyene cyclization and catalytic enantioselective intramolecular carbonyl-ene reaction with high enantioselectivities are described. The relationship and mechanistic differences between the two enantioselective reactions are analyzed.

Intramolecular Diels-Alder cycloaddition of N-substituted oxazolone triene has allowed direct entry to the functionalized octahydroquinoline. The manipulation of the framework by stereo- and regioselective introduction of the 5-methyl substituent, followed by excision of the carbamate, has produced ([plusmn])-2-epi-pumiliotoxin C.

A convenient and high-yielding three-step synthesis approach was developed to produce the simplest branched triene, [3]dendralene. The robust and operationally simple synthesis facilitated the synthesis of the volatile hydrocarbon in pure, solvent free form on a multigram scale without any involvement of chromatography, protecting groups or specialized equipment.

The article discusses a new host-guest strategy, which is used for the single-crystal-to-single-crystal topochemical polymerizations for the production of polymers from diacetylenes and trienes. The approach is shown to be extremely useful for the perfect crystalline formation of the polymers.

New strategies are described by using chiral acetal or chiral mixed-acetal in the presence of Lewis acids (Sn[Cl.sub.4] or Ti[Cl.sub.4]) in order to promote polyene cyclization reaction. Diverse optically active terpenoids are synthesized in few steps via simple modification sequences and an oxocarbenium intermediate is shown to be responsible for the good asymmetric selectivity for this type of reaction.

Study conducted shows that the solvatochromic behavior of polyenes depends on the polarizability of the medium and their solvatochromism increases markedly with increasing length of the polyene chain. The extreme sensitivity of polyenes to the polarizability of their environment is consistent with the fact that changes in molecular architecture give rise to polarizability gradients resulting in red shifts.

A novel and selective method is used for the synthesis of 8-methylenespiro[4,5]trienes via intramolecular electrophilic ipso-iodocyclization of N-(4-methylphenyl)propiolamides. Both the iodo and methylene group products obtained, provide a useful pathway to generate new groups for the synthesis of new bioactive products.

The effect of intermolecular dipole-dipole interactions on Raman spectra of polyconjugated molecules and also the behavior of push-pull polyenes are analyzed. Density functional theory (DFT) calculations are in good agreement with the mathematical models that are used for predicting the effect of intermolecular interactions on the vibrational spectra.

A novel collection of B-protected haloalkenylboronic acid building blocks [BB.sub.1]-[BB.sub.3] that are stable to purification and storage and highly selective toward a wide range of cross-coupling reactions is presented. The stability is maintained in the resulting polyenyl N-methyliminodiacetic acid (MIDA) boronate ester intermediates, thus enabling the simple, efficient and modular construction of polyene natural products with higher-order functions.

A catalytic asymmetric process is described for a Pd(0)-catalyzed regio- and stereoselective diamination of conjugated dienes and trienes. The resulting diamination products are important intermediates for the synthesis of various optically active compounds such as diamine, 2,3-diamino acid.

A series of polyene amide analogues are synthesized and structure-activity studies are done for the inhibition of bovine heart mitochondrial complex I. Findings reveal that this study gives the first detailed characterization of polyene amides as complex I inhibitors.

A concise and convergent total synthesis of the highly cytotoxic marine natural products iejimalide A-D (1-4) is reported. The iejimalides hence constitute an important new class of probe molecules for chemical biology in addition to their role as promising lead structures for the development of novel anticancer agents.

Intramolecular Diels-Alder reaction was used as a key step to stereoselectively synthesize coronafacic acid, a natural component of the phytotoxin coronatin. The coronafacic acid was isolated in a six-step sequence in 29% overall yield.

The controversy related to experiments implying that the [S.sub.1] states of longer polyenes have local energy minima, corresponding to a range of conformations and isomers separated by relatively low (2-4 kcal) barriers is reevaluated. Low barriers to isomerization and conformational change might account for the complex kinetics of [S.sub.2] -->[S.sub.1] nonradiative decay in carotenoids.

A study is conducted on the structure of cylindramide A, a macrocyclic tetramic and isolated from the sponge Halichondria cylindrata that is cytotoxic to B16 melanoma cells with an IC(sub 50) of 0.8 mug mL(super -1). It is concluded that a synthesis of cylindramide A is delineated that proceeds in 19 steps which is the longest linear sequence and highlights the utility of the tandem ring-opening-ring-closing-cross metathesis of simple norbornenes in the context of complex natural products synthesis.

4-(Dimethylamino)-4'-cyano-1,4-diphenylbutadiene (DCB) and 4-(dimethylamino)-2,6-dimethyl-4'-cyano-1,4-diphenylbutadiene (DMDCB) are characterized spectroscopically. The strong difference in absorption and fluorescence solvatochromic slopes suggests that the simple Onsager model with a point dipole approximation is not sufficient.

Time-dependent Hartree-Fock theory is used to study the electronic optical response of a series of linear polyene cations (+1 and +2) in strong laser fields. For a given molecule and fixed charge state, the degree of nonadiabatic coupling and excitation is greater for geometries with lower excitation energies.

Quantitative measurements of the resonance Raman cross sections and resonance hyper-Rayleigh and hyper-Raman hyperpolarizabilities for 3[5] in dilute acetone solution are reported and computational simulations of the linear absorption, hyper-Rayleigh, resonance Raman (RR), and resonance hyper-Raman (RHR) profiles is presented. The quantitative analysis of the RR and RHR intensity, and, similarity of their spectra in the region of a single electronic resonance supports the relatively small importance of the vibrational paths.

The original measurements of the single-molecule conductance of a carotenoid polyene were made by inserting the molecule into an alkanethiol self-assembled monolayer and contacting the inserted molecules either directly with a conducting atomic force microscope (AFM) probe or by using a gold nanoparticle as an intermediate contact. The electronic decay constant for carotenoid polyenes is measured, finding a value in good agreement with results of electronic structure calculations.

A new example is provided of completely diastereoselective polycyclization, affording the octahydrophenanthrene framework. The carbocation is generated by anchimerically assisted regiospecific protonation of a double bond adjacent to the iron tricarbonyl diene moiety.

An asymmetric Lewis acid-mediated intermolecular acetal-initiated cationic polyene cyclization to form tricyclic compounds is described. Optical active terpenes can be prepared in two-step modification sequence.