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21.
The oxidation of geminal biaryl ethenes 3 and 1,3-enynes 5 using m-chloroperbenzoic acid in dichloromethane at room temperature presents a catalyst-free approach for the synthesis of functionalized benzophenones 4 and ynones 6, respectively. 相似文献
22.
Conformational structure of peptides containing dehydroalanine: Formation of β‐bend ribbon structure
Fateh S. Nandel Nandita Malik Balvinder Singh D. V. S. Jain 《International journal of quantum chemistry》1999,72(1):15-23
α,β‐Unsaturated amino acids (dehydroamino acids) have been found in naturally occurring antibiotics of microbial origin and in some proteins. Due to the presence of the CαCβ double bond, the dehydroamino acids influence the main‐chain and the side‐chain conformations. The lowest‐energy conformational state of the model tripeptides, Ac–X–ΔAla–NHMe, (X=Ala, Val, Leu, Abu, or Phe) corresponds to ϕ1=−30°, ψ1=120° and ϕ2=ψ2=30°. This structure is stabilized by the hydrogen bond between CO of the acetyl group and the NH of the amide group, resulting in the formation of a 10‐membered ring. In the model heptapeptide containing ΔAla at alternate position with Ala, Abu, and Leu, the lowest‐energy conformation corresponds to ϕ=−30° and ψ=120° for all the Ala, Abu, and Leu residues and ϕ=ψ=30° for all ΔAla residues. A graphical view of the molecule in this conformation reveals the formation of three hydrogen bonds involving the CO moiety of the ith residue and the NH moiety of the i+3th residue, resulting in a 10‐membered ring formation. In this structure, only alternate peptide bonds are involved in the intramolecular hydrogen‐bond formation unlike the helices and it has been named the β‐bend ribbon structure. The helical structures were predicted to be the most stable structures in the heptapeptide Ac–(Aib–ΔAla)3–NHMe with ϕ=±30°, ψ=±60° for Aib residues and ϕ=ψ=±30° for ΔAla residues. The computational results reveal that the ΔAla residue does not induce an inverse γ‐turn in the preceding residue. It is the competitive interaction of small solvent molecules with the hydrogen‐bonding sites of the peptide which gives rise to the formation of an inverse γ‐turn (ϕ1=−54°, ψ1=82°; ϕ2=44°, ψ2=3°) in the preceding residue to ΔAla. The computational studies for the positional preference of ΔAla in the peptide containing one ΔAla and nine Ala residues reveals the formation of a 310 helical structure in all the cases with the terminal preferences for ΔAla, consistent with the position of ΔAla in the natural antibiotics. The extended structures is found to be the most stable for poly‐ΔAla. ©1999 John Wiley & Sons, Inc. Int J Quant Chem 72: 15–23, 1999 相似文献
23.
2H-Pyran-2-ones are useful precursors for the synthesis of various aromatic and heterocyclic compounds. In this Letter, we describe substituent-controlled direct access to functionalized 4-(2-oxo-1,2-diarylethyl)-5,6-diaryl-pyran-2-ones by stirring a mixture of 3-cyano-5,6-diaryl-2H-pyran-2-ones and functionalized deoxybenzoins through an unusual decyanation reaction. Under similar reaction conditions, the reactions of 3-carbomethoxy-5,6-diaryl-2H-pyran-2-ones with either substituted acetophenones or deoxybenzoins led to the synthesis of pyrano[3,4-c]pyran-1,8-diones in excellent yields. 相似文献
24.
Fateh Veer Singh 《Tetrahedron letters》2006,47(44):7767-7770
Aromatic compounds derived from two or more ‘isoprene units’ are the core structures found in several natural products of biological importance. Among them, cymene derivatives are of particular interest due to the unique structural and biological properties associated with them. In this letter, we describe an expeditious synthesis of cymene-cored unsymmetrical biaryls functionalized with donor and acceptor substituents prepared in excellent yields by the carbanion-induced ring transformation of 2H-pyran-2-ones with ketones. 相似文献
25.
An expeditious synthesis of several 2-amino-isophthalonitriles and their biaryl compounds is described and illustrated by carbanion-induced ring transformation of functionalized 2H-pyran-2-ones with malononitrile in excellent yields. The strength of the reaction lies in the creation of an aromatic ring at room temperature from six-membered lactones under mild reaction conditions. This approach is an alternative to Diels-Alder reactions of 2H-pyran-2-ones with dienophiles, which require forcing thermal conditions to obtain benzene derivatives. 相似文献
26.
An ultrasound-assisted synthesis of functionalized vinylic chlorides is described by palladium-catalyzed cross-coupling reaction of potassium aryltrifluoroborate salts and (Z)-2-chloro vinylic tellurides. This procedure offers easy access to vinylic chlorides architecture that contains sterically demanding groups in good yields. 相似文献
27.
Srivastava Isha Singh Fateh Kotia Ankit Ghosh Subrata Kumar 《Journal of Thermal Analysis and Calorimetry》2022,147(1):73-93
Journal of Thermal Analysis and Calorimetry - Quality of engine oil plays vital role in reducing frictional energy loss and enhancing durability. Recently, concept of nanolubricants, which is the... 相似文献
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29.
Mohammad Mehdi Fateh 《Nonlinear dynamics》2010,61(4):655-666
This paper focuses on the uncertainty bound parameter (UBP) to design the robust control of electrical manipulators. The UBP
is commonly obtained by considering the worst case of uncertainties in bounding functions. However, too high estimation of
UBP may cause saturation of input, higher frequency of chattering in the switching control laws, and thus a bad behavior of
the whole system, while too low estimation of UBP may cause a higher tracking error. A proper UBP is preferred to improve
the performance of robust control system. A simple, less dependent and proper UBP is proposed based on the nominal model of
electrical manipulator and feedbacks of joint accelerations. This work is motivated by recent experimental results in measuring
acceleration by optical encoder. Modeling of an electrical manipulator with presence of uncertainties is presented for control
purposes. The proposed robust control is justified by stability analysis. 相似文献
30.
Ayuob Aghanejad Amir R. Jalilian Yousef Fazaeli Davood Beiki Behrooz Fateh Ali Khalaj 《Journal of Radioanalytical and Nuclear Chemistry》2014,299(3):1635-1644
In order to develop a possible C-X-C chemokine receptor type 4 (CXCR4) imaging agent for oncological scintigraphy, [62Zn]labeled 1,1′-[1,4-phenylenebis(methylene)]bis-1,4,8,11-tetraazacyclotetradecane ([62Zn]-AMD3100) was prepared using in-house made [62Zn]ZnCl2 and AMD-3100 for 1 h at 50 °C (radiochemical purity: >97 % ITLC, >96 % HPLC, specific activity: 20–22 GBq/mmol) in acetate buffer. The complex showed highly hydrophilic properties (log P = ?1.114). Stability of the complex was checked in presence of human serum (37 °C) and in final formulation for 1 day. The biodistribution of the labeled compound in vital organs of wild-type Sprague–Dawdley rats were determined and compared with that of free Zn2+ cation up to 6 h. Co-incidence imaging of the complex was consistent with the distribution data up to 3 h. The complex can be a possible in vivo generator compound for PET imaging in CXCR4 positive tumors. 相似文献