Optically active (2RS,3S)-2-(ethanediyldioxyethyl)-3-methylpentanal (1) and (3RS,4S)-4-methyl-3-(N-methylthiazolidine-2-yl)-hexanal (2) were prepared from (3RS,4S)-4-methyl-3-(N-methyl-thiazolidine-2-yl)-1,1-ethanediyldioxyhexane. 相似文献
Microwave technique has been utilised in the preparation of β-keto esters. Two different procedures are described: transesterification of β-keto esters and ring opening of 2,2,6-trimethyl-1,3-dioxin-4-one. 相似文献
We report the synthesis and characterization of a water‐soluble, star‐shaped macromolecular platform consisting of eight β‐cyclodextrin (β‐CD) units anchored to the narrower rim of a γ‐CD core through bis(triazolyl)alkyl spacers. The efficient synthetic protocol is based on the microwave (MW)‐promoted Cu‐catalyzed 1,3‐dipolar cycloaddition of CD monoazides to CD monoacetylenes. The ligand‐hosting capability of the construct has been assessed by relaxometric titration and nuclear magnetic relaxation dispersion (NMRD) profiling, which showed it to be good, and this was supported by molecular dynamics simulations. To demonstrate the feasibility of obtaining supramolecular structures with high hosting ability, we designed a dimeric platform, formed by joining two nonamers through the γ‐CD cores through a bis(lithocholic acid) linker. With a view to the potential biological applications, cytotoxicity and extent of binding to human serum albumin were assessed. The properties of this dendrimeric multicarrier make it suitable for pharmaceutical and diagnostic purposes, ranging from targeted drug delivery to molecular imaging. 相似文献
Conjugation of a hydrophobic poly(2‐oxazoline) bearing tertiary amide groups along its backbone with a short single stranded nucleotide sequence results in an amphiphilic comb/graft copolymer, which organizes in fibrils upon direct dissolution in water. Supported by circular dichroism, atomic force microscopy, transmission electron microscopy, and scattering data, fibrils are formed through inter‐ and intramolecular hydrogen bonding between hydrogen accepting amide groups along the polymer backbone and hydrogen donating nucleic acid grafts leading to the formation of hollow tubes.
Propolis is a balsamic product obtained from vegetable resins by exotic Africanized bees Apis mellifera L., transported and processed by them, originating from the activity that explores and maintains these individuals. Because of its vegetable and natural origins, propolis is a complex mixture of different compound classes; among them are the volatile compounds present in the aroma. In this sense, in the present study we evaluated the volatile fraction of propolis present in the aroma obtained by distillation and simultaneous extraction, and its chemical composition was determined using coupled gas chromatography, mass spectrometry, and flame ionization detection. The majority of compounds were sesquiterpene and hydrocarbons, comprising 8.2–22.19% α-copaene and 6.2–21.7% β-caryophyllene, with additional compounds identified in greater concentrations. Multivariate analysis showed that samples collected from one region may have different chemical compositions, which may be related to the location of the resin’s production. This may be related to other bee products. 相似文献
Twelve naphthochromenone photocatalysts (PCs) were synthesized on gram scale. They absorb across the UV/Vis range and feature an extremely wide redox window (up to 3.22 eV) that is accessible using simple visible light irradiation sources (CFL or LED). Their excited‐state redox potentials, PC*/PC.? (up to 1.65 V) and PC.+/PC* (up to ?1.77 V vs. SCE), are such that these novel PCs can engage in both oxidative and reductive quenching mechanisms with strong thermodynamic requirements. The potential of these bimodal PCs was benchmarked in synthetically relevant photocatalytic processes with extreme thermodynamic requirements. Their ability to efficiently catalyze mechanistically opposite oxidative/reductive photoreactions is a unique feature of these organic photocatalysts, thus representing a decisive advance towards generality, sustainability, and cost efficiency in photocatalysis. 相似文献
Predictability is a key requirement to encompass late‐stage C?H functionalization in synthetic routes. However, prediction (and control) of reaction selectivity is usually challenging, especially for complex substrate structures and elusive transformations such as remote C(sp3)?H oxidation, as it requires distinguishing a specific C?H bond from many others with similar reactivity. Developed here is a strategy for predictable, remote C?H oxidation that entails substrate binding to a supramolecular Mn or Fe catalyst followed by elucidation of the conformation of the host‐guest adduct by NMR analysis. These analyses indicate which remote C?H bonds are suitably oriented for the oxidation before carrying out the reaction, enabling prediction of site selectivity. This strategy was applied to late‐stage C(sp3)?H oxidation of amino‐steroids at C15 (or C16) positions, with a selectivity tunable by modification of catalyst chirality and metal. 相似文献