Asymmetric multicomponent reactions: diastereoselective synthesis of substituted pyrrolidines and prolines

A novel diastereoselective synthesis of substituted pyrrolidines has been developed. Asymmetric multicomponent reactions of optically active phenyldihydrofuran, N-tosyl imino ester, and silane reagents in a one-pot operation afforded highly substituted pyrrolidine derivatives diastereoselectively. The reaction is quite efficient and constructed up to three stereogenic centers in a single operation.     

A facile strategy for synthesis of α,α′‐heterobifunctionalized poly (ε‐caprolactones) and poly (methyl methacrylate)s containing “clickable” aldehyde and allyloxy functional groups using initiator approach

Two new initiators, namely, 4‐(4‐(2‐(4‐(allyloxy) phenyl)‐5‐hydroxypentane 2‐yl) phenoxy)benzaldehyde and 4‐(4‐(allyloxy) phenyl)‐4‐(4‐(4‐formylphenoxy) phenyl) pentyl 2‐bromo‐2‐methyl propanoate containing “clickable” hetero‐functionalities namely aldehyde and allyloxy were synthesized starting from commercially available 4,4′‐bis(4‐hydroxyphenyl) pentanoic acid. These initiators were utilized, respectively, for ring opening polymerization of ε‐caprolactone and atom transfer radical polymerization of methyl methacrylate. Well‐defined α‐aldehyde, α′‐allyloxy heterobifunctionalized poly(ε‐caprolactones) (M_n,GPC: 5900–29,000, PDI: 1.26–1.43) and poly(methyl methacrylate)s (M_n,GPC: 5300–28800, PDI: 1.19–1.25) were synthesized. The kinetic study of methyl methacrylate polymerization demonstrated controlled polymerization behavior. The presence of aldehyde and allyloxy functionality on polymers was confirmed by ¹H NMR spectroscopy. Aldehyde‐aminooxy and thiol‐ene metal‐free double click strategy was used to demonstrate reactivity of functional groups on polymers. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Asymmetric multi-component reactions: convenient access to acyclic stereocenters and functionalized cyclopentenoids

Asymmetric multi-component reactions of optically active phenyl dihydrofuran, keto ester or N-tosyl imino ester, and allylsilane provided functionalized phenyl tetrahydrofurans with multiple stereogenic centers diastereoselectively. Cleavage of the resulting substituted tetrahydrofurans readily provided acyclic derivatives with three contiguous asymmetric centers via an acyloxycarbenium ion intermediate. Ring closing olefin metathesis, using Grubbs catalyst, afforded functionalized cyclopentene derivatives in optically active form. A one pot tandem tetrahydrofuran ring cleavage followed by ring closing olefin metathesis also provided functionalized cyclopentenes in good yield.     

High-Performance Thin-Layer Chromatographic Determination of Aceclofenac in the Bulk Drug and in Pharmaceutical Preparations

JPC – Journal of Planar Chromatography – Modern TLC -     

Quasi-affine symmetric designs

A symmetric design with parameters v = q ²(q + 2), k = q(q + 1), λ = q, q ≥ 2, is called a quasi-affine design if its point set can be partitioned into q + 2 subsets P ₀, P ₁,..., P _q , P _q+1 such that the induced structure in every point neighborhood is an affine plane of order q (repeated q times). A quasi-affine design with q ≥ 3 determines its point neighborhoods uniquely and dual of such a design is also a quasi-affine design. These structural properties pave way for definition of a strongly quasi-affine design and it is also shown that associated with every quasi-affine design is a unique strongly quasi-affine design from which the given quasi-affine design is obtained by certain unique cutting and pasting operation. This investigation also enables us to associate a unique 2-regular graph with q + 2 vertices and in turn, a unique colored partition of the integer q + 2. These combinatorial consequences are finally used to obtain an exponential lower bound on the number of non-isomorphic solutions of such symmetric designs improving the earlier lower bound of 2. Work of Sanjeevani Gharge is supported by Faculty Improvement Programme of U.G.C., India.     

DMSO–POCl3: a reagent for methylthiolation of imidazo[1,2-a]pyridines and other imidazo-fused heterocycles

A practical and metal free method for methylthiolation of imidazo[1,2-a]pyridines and other imidazo-fused heterocycles using DMSO–POCl₃ complex is reported. The reactions are carried out at room temperature that give the corresponding methylthiolated products in good to excellent yield. Further, its application to indole has been demonstrated.     

Rental price and rental duration under retail competition

Consider a retailer that rents products to customers for a pre-specified rental duration. By considering the dynamics of uncertain rental demand and return processes, we first present a base model that is intended to analyze the impact of rental duration on the stocking level, the rental price, and the retailer’s profit. Due to the complexity of the base model, we develop an approximation scheme to obtain tractable results. Also, we apply the base model to analyze a situation in which a retailer enters a revenue sharing agreement with a distributor. Moreover, we expand our base model to address the issue of competition in rental duration and rental price. The analysis of our competitive model in a duopolistic environment suggests that the market equilibrium depends on the market potential and the rental duration sensitivity. Furthermore, we establish conditions under which one firm will charge a lower rental price while the other firm will offer a longer rental duration in equilibrium.     

Self tapering and uptapering of a self guided laser beam in an absorbing/gain medium with nonlinearity

The absorption/gain induced self tapering and uptapering of a self guided Gaussian laser beam when the beam propagates in a saturable nonlinear medium has been discussed. Using the WKBJ and abberationless paraxial ray approximation a beam width equation has been derived. Conditions for tapering/uptapering for both cases i.e., for absorption and gain have been discussed. The beam width of tapered/uptapered beam depends on the rate of absorption/gain, and the length of absorption/gain region along the beam propagation direction. The importance of the present study is pointed out.     

Auftrennung der Proteine der Alge Chlorella

Zusammenfassung Die wasserlöslichen Proteine aus der einzelligen süßwasseralge Chlorella pyrenoidosa wurden nach Homogenisierung der Zellen erhalten. Die Proteine wurden dann einerseits durch Chromatographie auf DEAE-Zellulose, gefolgt von Elektrophorese in Polyacrylamid-Gel, und anderseits durch Gel-Filtration in Sephadex G-200 fraktioniert. Man findet, daß die Proteine nach elektrischer Ladung und Molekulargewicht aus vielen Komponenten bestehen. Einige dieser Komponenten lassen sich jedoch durch die Methode der kombinierten Chromatographie und Elektrophorese charakterisieren. Wesentliche Gehalte an Nukleinsäure wurden bei der Chromatographie nur in der letzten — am schwersten eluierbaren — Fraktion gefunden. Dagegen ist die Nukleinsäure bei der Gel-Filtration über mehrere Fraktionen verteilt.

---

The water soluble proteins of the unicellular freshwater alga Chlorella pyrenoidosa were obtained after homogenization of the cells. The proteins were then fractionated either by DEAE chromatography, followed by electrophoresis in polyacrylamide gel, or by gel filtration in Sephadex G-200. The proteins were found to consist of many components differing in electric charge and molecular size. Some of these components may be characterized by combined chromatography and electrophoresis. Appreciable amounts of nucleic acid have been found in chromatography only in the fraction eluted last. In contrast, in gel filtration nucleic acid is distributed over several fractions.

---

---

Mit 5 Abbildungen