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Five novel 1,1'-binaphthalene analogues

The influence factors of surfactant-type catalysts system on the asymmetric transfer hydrogenation (ATH) of ketones in water, including the length of aliphatic tail, the concentration of catalysts and the solvent, have been investigated. These factors played significant roles on reaction activity and stereo control. With single-chain surfactant-type catalyst Rh-L4, α, β-unsaturated ketones especially the aliphatic derivatives affords excellent regioselectivities and enantioselectivities.

Quinone methide (QM) formation induced by endogenously generated H2O2 is attractive for biological and biomedical applications. To overcome current limitations due to low biological activity of H2O2-activated QM precursors, we are introducing herein several new arylboronates with electron donating substituents at different positions of benzene ring and/or different neutral leaving groups. The reaction rate of the arylboronate esters with H2O2 and subsequent bisquinone methides formation and DNA cross-linking was accelerated with the application of Br as a leaving group instead of acetoxy groups. Additionally, a donating group placed meta to the nascent exo-methylene group of the quinone methide greatly improves H2O2-induced DNA interstrand cross-link formation as well as enhances the cellular activity. Multiple donating groups decrease the stability and DNA cross-linking capability, which lead to low cellular activity. A cell-based screen demonstrated that compounds 2a and 5a with a OMe or OH group dramatically inhibited the growth of various tissue-derived cancer cells while normal cells were less affected. Induction of H2AX phosphorylation by these compounds in CLL lymphocytes provide evidence for a correlation between cell death and DNA damage. The compounds presented herein showed potent anticancer activities and selectivity, which represent a novel scaffold for anticancer drug development.

A chiral double-chain surfactant-type ligand was designed and synthesized. The rhodium catalyst formed from the ligand can self-assemble into chiral vesicular aggregates in water, which was applied to the ATH of a broad range of aromatic ketoesters in neat water and gave up to 99% yield and 99% ee. In addition, this double-chain surfactant-type catalyst could also be applied to the dynamic kinetic resolution (DKR) of bicyclic β-ketoesters in water.

UV irradiation of several aryl boronates efficiently produced bifunctional benzyl cations that selectively form guanine-cytosine cross-links in DNA. Photoinduced homolysis of the C-Br bond took place with the aryl boronate bromides 3a and 4a, generating free radicals that were oxidized to benzyl cations via electron transfer. However, photoirradiation of the quaternary ammonium salts 3b and 4b led to heterolysis of C-N bond, directly producing benzyl cations. The electron-donating group in the aromatic ring greatly enhanced cross-linking efficiency.

Most recently, alkylation via photogenerated carbocations has been identified as a novel mechanism for photoinduced DNA interstrand cross-link (ICL) formation by bifunctional aryl compounds. However, most compounds showed a low efficiency for DNA cross-linking. Here, we have developed a series of new 1,1′-binaphthalene analogues that efficiently form DNA ICLs upon 350 nm irradiation via generated 2-naphthalenylmethyl cations. The DNA cross-linking efficiency depends on the substituents at position 4 of the naphthalene moiety as well as the leaving groups. Compounds with NO2, Ph, H, Br, or OMe substituents led to 2–4 times higher DNA ICL yields than those with a boronate ester group. Compounds with trimethylammonium salt as a leaving group showed slightly better cross-linking efficiency than those with bromo as a leaving group. Some of these compounds showed a better cross-linking efficiency than that of traditional alkylating agents, such as nitrogen mustard analogues or quinone methide precursors. These ...

Most photoinduced DNA cross-link formation by a bifunctional aryl derivative is through a bisquinone methide. DNA cross-linking via a bisarylcarbocation remains a less explored area. We designed and synthesized a series of naphthalene boronates that produce DNA interstrand cross-links via a carbocation upon UV irradiation. A free radical was generated from the naphthalene boronates with 350 nm irradiation and further converted to a carbocation by electron transfer. The activation mechanism was determined using the orthogonal traps, 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO) and methoxyamine that react with either the free radical or the carbocation but not both. This represents a novel example of photoinduced DNA cross-link formation via carbocations generated from a bisaryl derivative. This work provides information useful for the design of novel photoactivated DNA cross-linking agents.

A new flexible C1-symmetric tridentate ligand (S)-N-(2-(tert-butylsulfinyl)benzyl)-1-(pyridin-2-yl)methanamine sulfoxide (L1) was successfully prepared and utilized as a chiral ligand for Ir(I)-catalyzed ATH (asymmetric transfer hydrogenation) reactions. Without any cooperation of other chiral center, encouraging ee and conversion values have been achieved, which provide us a better understanding on these types of ligands and a new strategy to develop new high-efficiency chiral catalysts for asymmetric reaction.

A rhodium complex with an amphiphilic, chiral surfactant-type ligand is applied to the asymmetric transfer hydrogenation of long-chained aliphatic ketoesters.

A series of amphiphilic ligands were designed and synthesized. The rhodium complexes with the ligands were applied to the asymmetric transfer hydrogenation of broad range of long-chained aliphatic ketoesters in neat water. Quantitative conversion and excellent enantioselectivity (up to 99% ee) was observed for α-, β-, γ-, δ- and e-ketoesters as well as for α- and β-acyloxyketone using chiral surfactant-type catalyst 2. The CH/π interaction and the strong hydrophobic interaction of long aliphatic chains between the catalyst and the substrate in the metallomicelle core played a key role in the catalytic transition state. Synergistic effects between the metal-catalyzed site and the hydrophobic microenvironment of the core in the micelle contributed to high stereoselectivity.

As an efficient catalyst for asymmetric transfer hydrogenation reaction (ATH reaction) of α,β-unsaturated ketones, Rh-Cp ∗ –TsDPEN (Cp ∗ = 1,2,3,4,5-pentamethylcyclopenta-1,3-diene, TsDPEN = N -( p -toluenesulfonyl)-1,2-diphenyl- ethylenediamine) shows high chemoselectivity on C O and C C reduction. In our method, both C O and C C bonds in a variety of chromenone derivatives were reduced efficiently in aqueous media, resulting in at least 98% ee and up to 99% yields in a convenient way without further purification. The product was a useful intermediate for deriving chiral chroman-4-amine, which was reported as an effective agent against hypotension and inflammatory pain by inhibiting human bradykinin B1 receptor.

Accurate detecting and correcting Chinese grammar errors is the problem that many Chinese NLP research experts have been working on. However, Chinese grammars are complex and flexible. Collecting and Filtering the Chinese grammar errors with good popularity has been a major problem in this area. This paper presents an indexing method of Chinese grammar rules based on Corpus. With the corresponding searching system, we can evaluate the rules of the frequency and the accuracy. For each evaluated rule, we adopt an iterative approach to improve it for its better performance in the real world. Meanwhile, it also introduces the important role of corpus of this method. The test results on different corpus show that the feasibility and effectiveness of this method.

The title rhodium TsDPEN complex efficiently catalyzes the asymmetric transfer hydrogenation of chromenones to produce alcohols (II) with excellent enantioselectivities.