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Rambabu N. Reddi,Changbum Jo,Arumugam Sudalai 대한화학회 2022 Bulletin of the Korean Chemical Society Vol.43 No.10
This article describes a concise synthesis of two important fragments (tetrahydropyran [THP] and ketone moieties) of the cytotoxic macrolide (+)-neopeltolide in 10 long linear steps in enantiomerically pure form. Asymmetric Keck allylation to install the required C11 and C13 stereocenters, N-heterocyclic carbene (NHC)-catalyzed oxoacyloxylation to functionalize alkenes, and reductive oxa-Michael addition to construct 2,6-difunctionalized THP unit intramolecularly are the important steps in synthetic efforts. Finally, Keck asymmetric allylation and Lewis acid-catalyzed diastereoselective allylation of the aldehyde were sequentially employed to establish the stereocenters at C11 and C13 positions, respectively.
Ramesh, B.,Dillip, G.R.,Reddy, G. Rajasekhara,Raju, B. Deva Prasad,Joo, S.W.,Sushma, N. John,Rambabu, B. Elsevier 2018 Optik Vol.156 No.-
<P><B>Abstract</B></P> <P>A high-temperature solid state reaction route was employed to synthesize the phosphate based new orange-red emitting trivalent samarium (Sm<SUP>3+</SUP>) ions doped calcium zinc phosphate (CZP: CaZn<SUB>2</SUB>(PO<SUB>4</SUB>)<SUB>2</SUB>) phosphor. The crystalline phase formation was studied by X-ray diffraction analysis. The surface properties of the phosphor were investigated by X-ray photoelectron spectroscopy. Under the excitation of 402 nm, the emission spectra of CZP:Sm<SUP>3+</SUP> has several peaks and the dominant peak at 596 nm was ascribed to <SUP>4</SUP>G<SUB>5/2</SUB> → <SUP>6</SUP>H<SUB>7/2</SUB> transition. The concentration quenching effect of Sm<SUP>3+</SUP> in CZP phosphor was observed for 5 at%. The mechanism of energy transfer between similar Sm<SUP>3+</SUP> ions was determined to be quadrupole-quadrupole interaction. The decay curves of all phosphors were well fitted to the first-order exponential function. The chromaticity coordinates were located in the orange-red region of the chromaticity diagram. Therefore, these results suggest that the orange-red emitting new CZP:Sm<SUP>3+</SUP> phosphor to be used in the phosphor-converted white light emitting diodes.</P>