2,3-Bis(trimethylsilyloxy)-1,3-butadiene as a useful reactive diene in the Diels-Alder reaction

Stereoselective Synthesis of trans-Decalin-Based Spirocarbocycles via Photocyclization of 1,2-Diketones

Diastereoselective synthesis of the trans-decalin-based α-hydroxyl butanone spirocarbocycles bearing all-carbon quaternary stereogenic centers has been achieved via Norrish-Yang photocyclization of trans-decalin-substituted-2,3-butanediones using daylight. Density functional theory (DFT) calculations suggest that this diastereoselective reaction is affected by both substrate conformation and intramolecular hydrogen bonds. The developed chemistry could be applied to synthesizing the derivatives of the trans-decalin-based biologically important natural products.

2,3-Dimethoxy-2,3-dimethyl-1,4-dioxane as a useful precursor to 2,3-dimethylene-1,4-dioxane for [4+2] cycloaddition reaction

2,3-Dimethoxy-2,3-dimethyl-1,4-dioxane readily prepared from biacetyl serves as a stable precursor to 2,3-dimethylene-1,4-dioxane which undergoes a [4+2] cycloaddition reaction with dienophiles to give functionalized cyclohexene derivatives. The cycloaddition adducts obtained by the present procedure are transformed into potentially useful intermediates for biologically important materials.

2,3-Dimethoxy-2,3-dimethyl-1,4-dioxane serves as a stable precursor to 2,3-dimethylene-1,4-dioxane which undergoes a cycloaddition with dienophiles. The adducts are transformed into useful intermediates for biologically important materials.

Synthesis of Core-Modified Third-Generation Light-Driven Molecular Motors

The synthesis and characterization of a series of light-driven third-generation molecular motors featuring various structural modifications at the central aromatic core are presented. We explore a number of substitution patterns, such as 1,2-dimethoxybenzene, naphthyl, 1,2-dichlorobenzene, 1,1':2',1″-terphenyl, 4,4″-dimethoxy-1,1':2',1″-terphenyl, and 1,2-dicarbomethoxybenzene, considered essential for designing future responsive systems. In many cases, the synthetic routes for both synthetic intermediates and motors reported here are modular, allowing for their post-functionalization. The structural modifications introduced in the core of the motors result in improved solubility and a bathochromic shift of the absorption maxima. These features, in combination with a structural design that presents remote functionalization of the stator with respect to the fluorene rotors, make these novel motors particularly promising as light-responsive actuators in covalent and supramolecular materials.

Photochemically Produced Aminocyclobutanes as Masked Dienes in Thermal Electrocyclic Cascade Reactions

Cyclobutane products of a triplet sensitized enamide-alkene intramolecular [2 + 2] photocycloaddition have been shown to undergo fragmentation under acidic conditions. This lability has been exploited by inducing a complexity-generating thermal electrocyclic cascade sequence involving the in situ formation of a cyclobutene, followed by electrocyclic ring opening, Diels-Alder cycloaddition, and subsequent lactamization. This combination of excited state photochemistry and thermal electrocyclic cascade reactions allows simple planar molecules to be rapidly transformed into sp³-rich scaffolds.

Mycobacterium aromativorans JS19b1(T) Degrades Phenanthrene through C-1,2, C-3,4 and C-9,10 Dioxygenation Pathways

Mycobacterium aromativorans strain JS19b1(T) can utilize phenanthrene as a sole source of carbon and energy. Strain JS19b1(T) degrades phenanthrene through highly branched metabolic pathways, including dioxygenation on C-1,2, C-3,4 and C-9,10 positions and ring opening by both ortho- and meta-cleavage. The presence of novel metabolic pathways was confirmed by replacement cultivation using synthetic metabolite standards. The metabolites were isolated and identified by gas chromatography-mass spectrometry. Both ortho and meta-cleavage products of 1,2- and 3,4-dihydroxyphenanthrene were detected. Two ortho-cleavage products, 1-[(E)-2-carboxyvinyl]-2-naphthoic acid and 2-[(E)-2-carboxyvinyl]-1-napthoic acid were further metabolized to naphthalene-1,2-dicarboxylic acid and then to 1,2-dihydroxynaphthalene, which can also be produced from the meta-cleavage products hydroxynaphthoic acids. These results suggest that part of the branched pathways is merged into 1,2-dihydroxynaphthalene. The concentrations of the products from C-9,10 dioxygenation were higher than those from other pathways. C-9,10 dioxygenation of phenanthrene produced phthalic acid through decarboxylation and mono-/di-oxygenation. The diverse phenanthrene metabolic pathways in JS19b1(T) give a new insight of the bacterial degradation of polycyclic aromatic hydrocarbons.

An expeditious approach toward the total synthesis of CP-263,114

[reaction: see text] Assembly of the carbocyclic core of CP-263,114 has been accomplished efficiently and in high yield. Key steps include a phenolic oxidation/intramolecular Diels-Alder sequence, tandem radical cyclization, and the late-stage fragmentation of a densely functionalized isotwistane skeleton.