Methods structural revision

Rychnovsky, S. D. Predicting NMR spectra by computational methods structure revision of hexacyclinol, Org. Lett. 2006, 8, 2895-2898. 

The use of UNIFAC for estimating activity coefficients in binary and multicomponent oiganic and oiganic—water systems is recommended for those systems composed of nonelectrolyte, nonpolymer substances for which only structural information is known. UNIFAC is not recommended for systems for which some reliable experimental data are available. The method, including revisions through 1987 (39), is available in commercial software packages such as AspenPlus (174). 

Bisbenzylisoquinoline alkaloids. Comprehensive tabulation of literature for 1978-1981 (Chemical Abstracts Volumes 88-95), with 164 references. Covers structure revisions, additional (mainly spectral) data on known alkaloids, new sources of known alkaloids, structures, properties, summarized confirmatory reactions of new alkaloids, and biosynthetic evidence. Alkaloids are tabulated by botanical sources and pharmacological activity. A section on methods (CD, luminescence spectra, specific rotation, TLC) is included. 

Holmes, K. C., and Blow, D. M. The Use of X-ray Diffraction in the Study of Protein and Nucleic Acid Structure. Revised reprint from Methods of Biochemical Analysts. (Ed., Glick, D.) 13, 113-239 (1966). Interscience (John Wiley) New York, London, Sydney (1966). Reprinted Krieger Melbourne, FL (1979). 

With the aid of the above structural revision of chondrocurine and mass and n.m.r. spectral analysis, the structure of the curine-type alkaloid chondrofoline (288 R = H) from Chondrodendron platyphyllum has been established.260 A simple method for the preparation of the C(4")-trideuteriomethoxy-compound (288 R = CD3) was also described. 

These optimization studies are an important step in the study of Simmons-Smith cyciopropanations since they allowed for the development of a selective, catalytic method for introduction of a simple methylene unit. However, they also provide insights into the basic mechanism of this process. Together with earlier studies regarding carbenoid structure, the true nature of the reactive carbenoid, lCH2Znl, was confirmed. On the basis of these results, a revised transition structure was proposed. Although there is no direct evidence for such a transition... 

The radial distribution method, while thus not completely independent of the usual visual method, is sufficiently different from it to lead in some cases to somewhat different values for interatomic distances. We feel that these values carry some weight, and we have accordingly discussed by the new method a number of molecules whose structures as determined by the usual visual method have been reported in earlier publications, and have then combined the results of the two methods in presenting a revised set of values of interatomic distances for these molecules. 

Revised Values of Double-Bond Covalent Radii.—This investigation has led to the value 1.34 A. for the carbon-carbon double-bond distance, 0.04 A. less than the value provided by the table of covalent radii.111 4 Five years ago, when this table was extended to multiple bonds, there were few reliable experimental data on which the selected values for double-bond and triple-bond radii could be based. The single-bond radii were obtained -from the study of a large number of interatomic distances found experimentally by crystal-structure and spectroscopic methods. The spectroscopic value of the triple-bond radius of nitrogen (in N2) was found to bear the ratio 0.79 to the single-bond radius, and this ratio was as-... 

Porphyrin is a multi-detectable molecule, that is, a number of its properties are detectable by many physical methods. Not only the most popular nuclear magnetic resonance and light absorption and emission spectroscopic methods, but also the electron spin resonance method for paramagnetic metallopor-phyrins and Mossbauer spectroscopy for iron and tin porphyrins are frequently used to estimate the electronic structure of porphyrins. By using these multi-detectable properties of the porphyrins of CPOs, a novel physical phenomenon is expected to be found. In particular, the topology of the cyclic shape is an ideal one-dimensional state of the materials used in quantum physics [ 16]. The concept of aromaticity found in fuUerenes, spherical aromaticity, will be revised using TT-conjugated CPOs [17]. 

DNA has two broad functions replication and expression. First, DNA must be able to replicate itself so that the information coded into its primary structure is transmitted faithfully to progeny cells. Second, this information must be expressed in some useful way. The method for this expression is through RNA intermediaries, which in turn act as templates for the synthesis of every protein in the body. The relationships of DNA to RNA and to protein are often expressed in a graphic syllogism called the central dogma. The concept was proposed by Crick in 1958 and was revised in 1970 to accommodate the discovery of the RNA-dependent DNA polymerase. Crick s original theory suggested that the flow of information was always from RNA to protein and could not be reversed, yet it allowed for the possibility of DNA synthesis from RNA. 

It also seems likely that some mental disorders (perhaps major depressive disorder) in their present form will fail to show evidence of taxonicity, but definitional refinement would help elucidate underlying taxa (e.g., melancholia). Thus, taxometrics may be able to serve as an impetus and a guide for revising the diagnostic system. Of course, taxometric methods alone are not sufficient to tackle this task and should be used in conjunction with dimensional methods, such as exploratory factor analysis. Dimensions provide the building blocks for construction of taxa, and research on the structure of psychopathology should integrate dimensional and taxometric methods. 

The borohydride reduction-periodate cleavage applied to 2,3-O-isopro-pylidene-D-ribono- 1,4-lactone (16a) led to L-erythrose (30). The method was also employed (31) for the synthesis of D-erythrose, starting from an Obenzylidene-D-ribonolactone. However, in this case, the structural assignments for the intermediate compounds must be revised, as the starting material formulated as 3,5-O-benzylidene-D-ribono-1,4-lactone (2) was, as discussed previously in this section, the 3,4-0-benzylidene-D-ribono-1,5-lactone (3a). Therefore, the correct structure for the product described as 3,5-O-benzylidene-D-ribitol (20, not isolated) would be 3,4-O-benzylidene-... 

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