Configuration Skeletal structure

Natalinine (491), C25H23N05, amorphous, is a minor alkaloid of Berberis empetrifolia Lam. MS and high-resolution NMR established the skeletal structure, and CD indicated the (R) configuration (561). Natalinine may be derived biogenetically from catabolism of an aporphine-benzylisoquinoline dimer [such as pakistanine (92), a major co-occurring alkaloid] (561), or by rearrangement of a coyhaiquine (107)-type dimer (562). 

Fig. 1. Skeletal structure for [Cu o-C6H4(TeMe)2l2] which has been shown by X-ray crystallography to adopt a meso configuration, but one that deviates significantly from ideal tetrahedral geometry.

Figure 11. Molecular modeling of aeanthifolin based on the skeletal structure and relative configuration determined by NMR left top tube model right top ball-and-stick model bottom space-filling model (H white C black 0 gray).

Moreover, the olfactory organ is able to deteet functional groups, structural characteristics such as skeletal structure (constitution), relative and absolute configuration. Therefore, the sense of smell is indeed regio-, stereo-, and enantioselective, as demonstrated by some typical examples. 

Solution to 47a Determine the configuration of the two asymmetric centers in the perspective formula. Now draw the skeletal structure, making sure the asymmetric centers have the same configurations they had in the perspective formulas. 

If you have access to a set of molecular models, converting between perspective formulas, Fischer projections, and skeletal structures is rather straightforward. If, however, you are interconverting these three-dimensional structures on a two-dimensional piece of paper, it is easy to make a mistake, particularly if you are not good at visualizing structures in three dimensions. Fortunately, there is a relatively foolproof method for these interconversions. All you need to know is how to determine whether an asymmetric center has the / or the 5 configuration (Sections 4.7 and 4.14). Look at the following examples to learn how easy it is to interconvert the various stractural representations. 

Converting a Fischer projection to a skeletal structure. Determine the configuration of the asymmetric centers in the Fischer projection, and then draw the skeletal structures using the same configuration for each of its asynunetric centers. 

Converting a skeletal structure to a perspective formula. Determine the configurations of the two asymmetric centers in the skeletal structure. Continue as described in Example 6 to arrive at the desired perspective formula. 

In addition to the effects of skeletal structure and of the chemical composition of the repeat units, the properties of a polymer are strongly influenced by its molecular microstructure. Variations in the geometric and configurational arrangements of the atoms in the repeat unit, and the distribution of these different spatial arrangements for the repeat units along the chain, are of particular importance. 

Draw skeletal structures of both configurational stereoisomers of lactic acid (shown in Model 2). 

Most products of solid-state (2 + 2) photodimerization are found to have skeletal configuration 66, while a few have configuration 67. This distribution clearly reflects the tendency of the monomers to crystallize in the particular corresponding structures. Reports (153) of solid-state photodimerizations that yield configuration 68 suggest that the range of product stereochemistries available via photodimerization is indeed large. 

The coset and Wigner subclass structures of the symmetric groups Sm permits to classify the regular PI°) of a given skeletal class of configurations in terms of processes and mechanisms 32a>c). 

The structural features of the solanum alkaloids are based on two primary skeletal configurations solanidane, with or without glycoside functionalities, as featured by the toxic and teratogenic steroidal alkaloids a-chaconine and a-solanine with the indolizidine type E-F ring (Figure 2.7a) and the spirosolane... 

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