Pseudo rings

ACS Symposium Series American Chemical Society Washington, DC, 1977. 

Pseudo rings are useful because they are the rings which are often formed in the construction of bridged molecules. 

There are usually certain bonds in a molecule whose disconnection in the retrosynthetic direction leads to a significant simplification of the cyclic structure. These are termed strategic bonds. Since these have been described in detail elsewhere, we shall consider them here only briefly.  

Other restrictions on strategic bonds prevent them from being aromatic and from leaving chiral side chains. These requirements are also based on current chemical technique. 

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The basic type I is represented by the 1 1 coordinatoclathrate of 20 DMSO 851 (Fig. 24). It is seen that an O—H. .. O interaction occurs between host and guest. Besides, one of the methyl C-atoms is proximal to the fixing —COOH thus forming a co-planar pseudo-ring arrangement of six non-H atoms (8-membered ring including... 

By this designation the four atom-four bond (three actual and one virtual) system should be regarded in much the same manner as the abbreviation PhH for the benzene ring (C6H6) in the metallocenes in Chapter 6. One difference, however, is that this functional symbol indicates not only that the pseudo-ring has two distinct forms (keto and enol) but also it canonically assigns locant numbers to the atoms, bonds and substituent R groups. 

It was suggested that a six-member chain of mannitol hexanitrate was coiled into a pseudo-ring. It is not surprising if one considers that long chain organic substances in solution have a tendency to be coiled. This is based on thermodynamical analysis, dipole measurements etc. 1124]. 

Conformational studies of clebopride and YM-08050 (20a) imply that it is the six-membered pseudo-ring, formed by the hydrogen bond between the amide proton and the ether oxygen atom, rather than the benzene... 

The chiroptical properties of pelletierine and anaferine have been studied. They reveal that both molecules are sensitive to conformational changes. The former apparently adopts the tra 5-pseudo-ring conformation (18) in acid solution and the c/5-fused counterpart (19) in neutral solution. The latter, in acid solution, shows a positive ellipticity for the n-ir carbonyl transition, of about the same magnitude as for (- )-pelletierine sulphate but opposite in sign, suggesting major conformational changes of unknown character. ... 

A variety of trap shapes have been proposed. In a first category, they are almost faithful reproductions of a classic trap, with electrodes approximating a ring and two end-cap electrodes. Some others have fewer electrodes their geometries are derived essentially either from a pseudo-ring or from end-cap electrodes. In all the cases, the shapes of the electrodes are easy to machine. 

Furet, P., Caravatti, G., Guagnano, V, Lang, M., Meyer, T, and Schoepfer, J. (2008) Entry into a new class of protein kinase inhibitors by pseudo-ring design. Bioorganic 6j Medicinal Chemistry Letters, 18, 897-900. 

To provide sufficient rigidity to the core at least two ring systems are usually required. Rare exceptions are the 2,4-alkyldienoic carboxylic acids in which dimers are formed by hydrogen bonding of the carboxylic acid groups (which becomes a pseudo-ring system) indeed, most carboxylic acid systems behave in the same manner, e.g., 4-alkoxybenzoic acids (6). 

Ar above or under the pseudo-ring plane near S Other centrifugal distortion constants fixed to the normal species value. 

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