The efficient syntheses of the ABCD ring system of the originally proposed structure of azaspiracid-1 and the ABCDE ring system of the revised structure of azaspiracid-1 containing the correct stereochemistry at C₆, C₁₀, ...

A 14-membered macrocycle with an allene and a furan strategically located at across the ring from each other is synthesized using an allene ring closing metathesis reaction. Upon treatment of the macrocycle with a catalytic amount of Pd(OAc)₂ and other additives, the first transannular [4+3] cycloaddition occurred to yield 37% of a ...

Complex ABCD field transformations are investigated for inhomogeneous optical ring cavities with losses and gain. It is shown that the sets of eigenfunctions, corresponding to counterpropagating waves, are really biorthogonal: the functions in each of these sets are really orthogonal relative to one another, and have a complex weighting factor independent ...

The binding of N-acetylglucosamine oligosaccharides (NAGn, n = 2-6) to hen egg-white lysozyme (HEWL; EC 3.2.1.17) was investigated by X-ray powder diffraction at room temperature. Each NAGn examined was found to bind to lysozyme in rapid-precipitation preparations in 1.0 M NaCl pH 6.0 buffer. The location of each NAGn was easily found from difference Fourier maps generated from ...

A palladium-catalyzed (3 + 2) cycloaddition of a vinylcyclopropane and a ?-nitrostyrene is employed to rapidly assemble the cyclopentane core of the Melodinus alkaloids. The ABCD ring system of the natural product family is prepared in six steps from commercially available materials. PMID:21786746

Because of their varied physiological activity, steroids are important testing grounds on which to explore the utility of novel synthetic methodology. In this study cobalt, in the form of CpCo(CO)/sub 2/ is used as a matrix around which to assemble natural and unnatural polycyclic products, including the steroid nucleus. In this way, the total synthesis of A-ring aromatic ...

The Huygens integral, or Green's function, for paraxial beam propagation in a generalized lenslike medium is derived as a Feynman path integral involving a summation over real rays. This formulation provides a physically intuitive understanding of the structure of the Green's function. The path integral is evaluated by introducing in a consistent manner the ...

We cloned the entire bphABCD genes encoding degradation of biphenyl and polychlorinated biphenyls to benzoate and chlorobenzoates from the chromosomal DNA of Pseudomonas putida KF715. The nucleotide sequence revealed two open reading frames corresponding to the bphC gene encoding 2,3-dihydroxybiphenyl dioxygenase and the bphD gene encoding ...

The authors cloned the entire bphABCD genes encoding degradation of biphenyl and polychlorinated biphenyls to benzoate and chlorobenzoates from the chromosomal DNA of Pseudomonas putida KF715. The nucleotide sequence revealed two open reading frames corresponding to the bphC gene encoding 2,3-dihydroxybiphenyl dioxygenase and the bphD gene encoding ...

A general approach to the regio- and stereoselective total synthesis of the benanomicin-pradimicin antibiotics (BpAs) is described. Construction of the aglycon has been achieved by 1) the diastereoselective ring-opening of a biaryl lactone by using (R)-valinol as a chiral nucleophile and 2) the stereocontrolled semi-pinacol cyclization of the aldehyde acetal by using SmI(2) in ...

... Title : The Structure of a Ring-D-Bridged Steroid,. ... Descriptors : (*STEROIDS, *MOLECULAR STRUCTURE), (*CRYSTAL STRUCTURE, STEROIDS ...

Braided Rings. Saturn's narrow F ring, just outside the main ring system, is a very complex structure. In this close-up view it is made up of two narrow bright rings ...

An ABCD formalism is identified to characterize a seeded Free Electron Laser (FEL) with three chirps: an initial frequency chirp in the seed Laser, an energy chirp in the electron bunch, and an intrinsic frequency chirp due to the FEL process. A scheme of generating attosecond few-cycle pulses is proposed by invoking an FEL seeded by high-order harmonic generation (HHG) from ...

This paper shows the structure of matrix near ring constructed over a weakly distributive and primative near ring. It is proved that a weakly distributive primitive near ring is a ring and the matrix near rings constructed over it is also a bag. (author)....

Results of an evaluation of support structures for the reactor vessel are reported. The U ring, box ring, integral ring, tee ring and tangential beam supports were investigated. The U ring is the recommended vessel support structure configuration.

The data returned by the Voyager on the Saturnian system has revealed the structure of Saturn's ring

Three syntheses of the architecturally complex, cytotoxic marine macrolide (+)-spongistatin 1 (1) are reported. Highlights of the first-generation synthesis include: use of a dithiane multicomponent linchpin coupling tactic for construction of the AB and CD spiroketals, and their union via a highly selective Evans boron-mediated aldol reaction en route to an ABCD aldehyde; ...

This document describes the Demos Ring component known as the Ring Closer (RC). A brief introduction to the Demos concept and the Ring communications structure and operation is given. The functions of the RC, as the unique element in the Ring, are defined...

... Accession Number : ADD311962. Title : STRUCTURE OF THE ACOUSTIC FIELD OF RING RADIATORS OF FINITE WIDTH. Corporate Author : ...