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81.
Roger D. Amos 《Chemical physics letters》1980,75(3):602-612
Møller-Plesset perturbation theory is used to find the second- and third-order correlation corrections to some oneelectron properties of HC1 and CO. An estimate of the fourth-order correction is made. It is shown that the perturbed wavefunctions can be constructed efficiently using the techniques of the direct CI methods. The results are comparable in accuracy with those obtained from large-scale CI calculations, but require considerably less computation. 相似文献
82.
83.
The kinetics of biomimetic mineralization at a fatty acid monolayer interface have been measured in situ by synchrotron x-ray reflectivity. The formation of biologically relevant amorphous calcium carbonate films is affected by soluble macromolecules, supersaturation rate of change, and Mg cations. We find that these solution conditions influence mineral film formation in a complementary fashion. Poly(sodium acrylate) extends the lifetime of metastable amorphous calcium carbonate, solution saturation controls the mineral film growth rate, and Mg cations create a longer induction time. This is the first quantification of potentially competitive biomineralization mechanisms that addresses nucleation and growth of the amorphous mineral phases, which are important in biomineralization. 相似文献
84.
Relativistic treatment of the spin-zero particles subject to the second Poschl-Teller-like potential
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The three-dimensional Klein-Gordon equation is solved for the case of equal vector and scalar second Poschl-Teller potential by proper approximation of the centrifugal term within the framework of the asymptotic iteration method. Energy eigenvalues and the corresponding wave function are obtained analytically. Eigenvalues are computed numerically for some values of n and It is found that the results are in good agreement with the findings of other methods for short-range potential. 相似文献
85.
We evaluate the Poynting vector generated by a heavy quark moving through a thermal state of N=4 gauge theory using the gauge-string duality. A significant diffusion wake is observed as well as a Mach cone. We discuss the ratio of the energy going into sound modes to the energy coming in from the wake. 相似文献
86.
In a quest to develop an effective, scalable synthesis of (+)-spongistatin 1 ( 1), we devised a concise, third-generation scalable synthesis of (+)- 7, the requisite F-ring tetrahydropyran aldehyde, employing a proline-catalyzed cross-aldol reaction. Subsequent elaboration to (+)-EF Wittig salt (+)- 3, followed by union with advanced ABCD aldehyde (-)- 4, macrolactonization and global deprotection permitted access to >1.0 g of totally synthetic (+)-spongistatin 1 ( 1). 相似文献
87.
88.
Ley SV Abad-Somovilla A Anderson JC Ayats C Bänteli R Beckmann E Boyer A Brasca MG Brice A Broughton HB Burke BJ Cleator E Craig D Denholm AA Denton RM Durand-Reville T Gobbi LB Göbel M Gray BL Grossmann RB Gutteridge CE Hahn N Harding SL Jennens DC Jennens L Lovell PJ Lovell HJ de la Puente ML Kolb HC Koot WJ Maslen SL McCusker CF Mattes A Pape AR Pinto A Santafianos D Scott JS Smith SC Somers AQ Spilling CD Stelzer F Toogood PL Turner RM Veitch GE Wood A Zumbrunn C 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(34):10683-10704
We describe in full the first synthesis of the potent insect antifeedant azadirachtin through a highly convergent approach. An O-alkylation reaction is used to unite decalin ketone and propargylic mesylate fragments, after which a Claisen rearrangement constructs the central C8-C14 bond in a stereoselective fashion. The allene which results from this sequence then enables a second critical carbon-carbon bond forming event whereby the [3.2.1] bicyclic system, present in the natural product, is generated via a 5-exo-radical cyclisation process. Finally, using knowledge gained through our early studies into the reactivity of the natural product, a series of carefully designed steps completes the synthesis of this challenging molecule. 相似文献
89.
Bagchi S Kim YS Charnley AK Smith AB Hochstrasser RM 《The journal of physical chemistry. B》2007,111(11):3010-3018
The linear infrared and two-dimensional infrared (2D IR) spectra in the amide-I region of N-acetyl tryptophan methyl amide (NATMA) in solvents of varying polarity are reported. The two amide-I transitions have been assigned unambiguously by using 13C isotopic substitution of the carbonyl group. The amide unit at the amino end shows a lower transition frequency in CH2Cl2 and methanol, while the acetyl end has a lower transition frequency in D2O. Multiple conformers exist in CH2Cl2 and methanol, but only one conformer is evident in D2O. The 2D IR cross peaks from the intermode coupling yield off-diagonal anharmonicities 2.5 +/- 0.5, 3.25 +/- 0.5, and 3.0 +/- 0.5 cm(-1) in CH2Cl2, methanol, and D2O, respectively, which by simple matrix diagonalization yield the coupling constants 8.0 +/- 0.5, 8.0 +/- 1.0, and 5.5 +/- 1.0 cm(-1). The major conformer in CH2Cl2 corresponds to a C7 structure, in agreement with that found in the gas phase [Dian, B. C.; Longarte, A.; Mercier, S.; Evans, D. A.; Wales, D. J.; Zwier, T. S. J. Chem. Phys. 2002, 117, 10688-10702] with intramolecular hydrogen bonding between the acetyl end C=O and the amino end N-H. The backbone dihedral angles (phi, psi) are determined to be in the ranges of (-55 +/- 5 degrees , 30 +/- 5 degrees ), (120 +/- 10 degrees , -20 +/- 10 degrees ), and (+/-160 +/- 10 degrees , +/-75 +/- 10 degrees ) in CH2Cl2, methanol, and D2O, respectively. 相似文献
90.
A highly convergent synthesis of (-)-okilactomycin is described. Key reactions of this synthesis include a strategy-level diastereoselective oxy-Cope rearrangement/oxidation sequence, a Petasis-Ferrier union/rearrangement tactic, and an efficient RCM reaction to construct the 13-membered macrocyclic ring. 相似文献