Fluorescent Properties of Cyanine Dyes As a Matter of the Environment.

In non-viscous aqueous solutions, the cyanine fluorescent dyes Cy3 and Cy5 have rather low fluorescence efficiency (the fluorescence quantum yields of Cy3 and Cy5 are 0.04 and 0.3, respectively [1, 2]) and short excited state lifetimes due to their structural features.

Quantitative High-Field NMR- and Mass Spectrometry-Based Fatty Acid Sequencing Reveals Internal Structure in Ru-Catalyzed Deuteration of Docosahexaenoic Acid.

Ru-based catalysis results in highly unsaturated fatty acid (HUFA) ethyl esters (EE) deuterated to various extents. The products carry H (D) mainly at their -allylic positions, where they are resistant to autoxidation compared to natural HUFA and are promising as neurological and retinal drugs. We characterized the extent of deuteration at each allylic position of docosa-4,7,10,13,16,19-hexaenoic acid deuterated to completion at -allylic and allylic positions (D-DHA) by two-dimensional (2D) and high-field (600 and 950 MHz) NMR.

Fluorescent Properties of Carboxyfluorescein Bifluorophores.

Bright fluorescent probes with enhanced intensities in the fluorescein channel are of great value for plenty of biological applications. To design effective probes one should introduce as many as possible fluorophores to the biomolecule while leaving its native structure as intact as possible. To reach this compromise, we designed and synthesized fluorescein bifluorophores on the 3,5-diaminobenzoic acid scaffold, which allows for insertion of two fluorophores at one modification site of a biomolecule.

Stereoselective synthesis of 2,6-trans-tetrahydropyrans.

A stereoselective route to the thermodynamically unfavorable 2,6-trans-tetrahydropyrans has been developed from coupling of hydroxyethyl-tethered cyclopropanols and aliphatic aldehydes. Noteworthy is high convergency from direct coupling of two segments.

Stereoselective cross-coupling between allylic alcohols and aldimines.

A cross-coupling reaction between an allylic alcohol and an imine is described for stereoselective allylation of aromatic and aliphatic imines. This method provides operationally simple, enantioselective access to functionalized homoallylic amines. Particularly noteworthy is direct use of a functionalized allylic alcohol as an allylating reagent without prederivatization, which obviates the use of preformed organometallic reagents or activated imine derivatives.

Low-valent titanium-mediated stereoselective alkylation of allylic alcohols.

We have developed low-valent titanium-mediated 1,3-transpositive cross-coupling reactions of acyclic and cyclic allylic alcohols for the stereoselective introduction of ethyl, 2-silylethyl, 2-phenethyl, and alkenyl groups. Cross-coupling of an allylic alcohol with a vinylsilane or styrene derivative is particularly noteworthy, as an efficient cross-selective coupling of two alkenes has been elusive. The stereochemistry of the cross-coupling alkylation is consistent with syn addition/beta-elimination.

Diastereoselective Prins-type reaction of cycloalkenylcyclopropanol silyl ethers and alpha,beta-unsaturated aldehyde acetals.

Electrophilic addition of 1-(1-cyclohexenyl)-1-cyclopropanol trimethylsilyl ether to alpha,beta-unsaturated aldehyde acetals under Lewis acidic conditions proceeds with good to excellent diastereoselectivity to afford spirocyclobutanones containing three contiguous stereocenters. A convenient entry to enantioselective syntheses is available by use of a nonracemic C2-symmetric acetal. Elaboration of the resulting adducts provides ready access to medium-sized carbocycles.

Use of cyclopropanols as conformational constraints in RCM.

[reaction: see text] Sequential application of the Kulinkovich cyclopropanation of carboxylic esters and RCM of the resulting cis-dialkenyl-tethered cyclopropanols provides an expedient route to functionalized medium-sized carbocycles. Subsequent elaboration of the cyclopropanol functionality, such as one-carbon ring expansion, to afford synthetically useful alpha,beta-enones is also worth noting.