Rings cyclohexenyl

Fig. 5.7 Stereoviews of the two forms of vitamin A acid 5-VI. Upper, triclinic form lower, monoclinic form. In both cases the view is on the plane of the three lower atoms of the cyclohexenyl ring. For clarity only oxygen atoms are labelled (From Bernstein 1987, with permission.)...

The cyclohexenyl ring and, to a lesser extent the cyclopen-tenyl and cycloheptenyl rings can possibly replace a phenyl ring. This is the case for the barbiturics cyclobarbital and heptabarbital which are entirely comparable to phenobarbital. From the metabolic point of view, the cyclohexenyl ring is oxidized in position a to the donble bond to produce the corresponding cyclohexenone (Figure 20.27). 

The cyclohexenyl ring and, to a lesser extent the cyclopente-nyl and cycloheptenyl rings can possibly replace a phenyl ring. This is the case for the barbiturics cyclobarbital... 

All the macrocyclic imines possess several characteristics in common (1) a six- or seven-membered imino ring (2) a cyclohexenyl ring with spiro linkage to the cyclo-imine (except for the prorocen-trolides with condensed rings) (3) para-substitution on the cyclohexenyl ring (4) a macrocycle... 

The aromatic ring of most chroman-substituted retinoids replaces C-5, C-6, C-7, C-8 and C-18 of the retinoic acid skeleton. However, the aromatic ring in novel nonatetraenoates (73)-(76) appears to replace the cyclohexenyl ring [C-l-C-6] of the retinoid skeleton as does the aromatic ring in acitretin (2). 

Flexible epoxy resins were synthesized by the polymerization of epoxy compounds in the presence of an unsaturated alcohol (Scheme 56) followed by the epoxidation of the double bond with PAA. If a glycidyl ether of a cyclohexenyl ring-containing alcohol is used as the epoxy compound, a polyether-epoxy resin is obtained (Scheme 57). The polymerization of 3-cyclohexenyl-1-methyl glyci-... 

An on-line hydrogenation method in conjunction with GC-MS was developed to correlate the mass spectra of the methyl esters of intact CFAM and their hydrogenated analogs (17). Ten CFAM from heated linseed oil were examined, and some tentative dienoic structures, with either cyclopentenyl or cyclohexenyl rings and a double bond of unknown location in the side chain, were suggested. 

The calculations indicated that the preference for either the chair- and/or the boat-like transition state is a consequence of the attempt to minimize non-bonding interactions between R and OMe with the cyclohexenyl ring substituents in the transition state. 

Fig. 2. Chemical structures of opiates. The antigenic determinant for immunoglobulin E antibodies is the N-methyl-cyclohexenyl ring in combination with a hydroxyl group on (modified from Bircher 1996)...

The regiochemistry of poly(CHD) is similar to that of poly( 1,3-butadiene) (PBD) 1,4- and 1,2-linked structures are shown in Scheme 18.2. For reference, the cis and trans possibilities for the 1,4-and 1,2-structures are also depicted. In this context, cis (or trans) denotes that the bridging C-C bonds between monomer units are in a cis (or trans) relationship on the face of the cyclohexenyl ring. In contrast to PBD, it is difficult to produce high molecular weight poly(CHD) solely through 1,2-addition because of monomer steric hindrance. 

Finally, it is noted that both kinamycin C and alter-salanol A contain an identical, polyoxygenated, cyclohexenyl ring which bears the potential leaving groups for quinone-methide formation. An analogous structural feature is also found in bostrycin, altersalanol B, and kinamycin A, B, and D. 

For several other retinoids, actual spectral data have not been published, but characteristic fragmentation patterns have been reported. These compounds include three urinary metabolites of retinoic acid in which the chain is shortened and the cyclohexenyl ring is oxidized (Hanni et al., 1976 see Fig. 7b, Chapter 11), three fecal metabolites of retinoic acid (4-oxoretinoic acid and two hydrox-ylated metabolites, see Fig. 6, Chapter 11 Hanni and Bigler, 1977), several metabolites (Hanni et al., 1972 see Fig. 14, Chapter 11) and isomers (Englert et al., 1978) of etretinate, 3-hydroxyanhydroretinol, a metabolite of 3-hy-droxyretinol (Barua et al., 1979), and a 4-oxo-Ci9 aldehyde metabolite of retinoic acid (Rockley et al., 1980 see Fig, 8, Chapter 11). With the advent of HPLC and an increase in the sensitivity of mass spectrometry, this technique should continue to be of great usefulness for the identification of retinoid metabolites. 

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