Search

An efficient 10-step preparation from 4-methoxypyridine of (2R,3R,4R)-2-acetamido-3,4-dihydroxy-piperidine ('XylNAc-isofagomine') in optically active form is described. Key steps include an enantioselective reduction with cateholborane/(S)-2-methyl-CBS-oxazaborolidine, and a stereoselective pseudo-glycosylation of lithium azide by a cyclic sulfite ester.

Optically active seleninate esters are obtained by chromatographic resolution on an optically active column. The reaction of the optically active seleninate ester and the sulfinate ester having bulky substituents with Grignard reagents is found to proceed with the retention of stereochemistry to give an optically active selenoxide and sulfoxides, respectively.

The synthesis of a series of optically pure benzo-, naptho-, and heterocycle-fused pyrollo[2,1-c]-[1,4]-diazepin-5,11-dione derivatives starting from L-proline methyl ester is presented. The presented general approach solves the need of starting from not very accessible amino aromatic starting materials, and its effectiveness is demonstrated in the synthesis of the antitumor antibiotic DC-81.

The fabrication and characterization of photovoltaic devices made from blends of (3,3'''-didodecylquaterthiophene) (PQT-12) and [6,6]-phenyl [C.sub.61] butyric acid methyl ester is described. The large difference in the power conversion efficiency (PCE) is due to the fact that blends with higher PQT-12 loading are transport limited, with much larger hole-to-electron mobility ratios.

The study of the ion-molecule reactions of 17 alkyl esters reacting with the common selection ion flow tube mass spectrometry (SIFT-MS) reagent ions, [H.sub.3][O.sup.+], [H.sub.3][O.sup.+]*[H.sub.2]O (n = 1,2,3), N[O.sub.+], and [O.sub.2.] is reported. The rearrangement of a protonated alkyl ester to form a parent protonated carboxylic acid is found to occur via an intramolecular rearrangement in the gas phase.

The study shows that boronic esters can easily be used as a system for crystallization-induced dynamic self-assembly equipped with an 'on-off' switch for equilibration. The system has the advantages of high yield, exquisite selectivity and a ready on-off ability and hence can be used for separation of compounds like naphthalene from other structurally similar compounds.

A series of stilbeneboronate pinacol cyclic esters, containing none to three nitro groups are synthesized by various olefination reactions and characterized by X-ray single crystal structure analysis. It is found that the UV-vis absorption of the fluoroboronates is strongly dependent on the solvents hydrogen-bond donating ability.

The stereocontrolled synthesis of multisubstituted and functionalized enol ethers through olefination is studied. It is noted that the development of first stereoselective olefination of esters affording tetrasubstituted, functionalized enol ethers are useful synthetic intermediates for various C-C bond formations.

Experiments are conducted for spectroscopic analysis of the allyl esters of some aromatic carboxylic acids. It is understood that these experiments allow the students to monitor the effect of hydrogen bonding on the IR stretching frequencies for the hydroxyl and carbonyl groups and also provide them with an excellent opportunity to examine the phenomenon of proton spin coupling in the NMR spectra of simple organic systems.

Photoinduced birefringence in a poly(malonic ester) containing two symmetrical p-cyanoazobenzene groups is investigated using two pumping beams with different wavelengths of 365 and 488 nm, which are assignable to the absorption wavelengths of trans and cis conformers of azobenzene, respectively.