Ring structures sidechain structure

The structures of ligands with phosphine substituents bound both to a cyclopentadiene ring and sidechain are shown in Figure 15.6. 

HP (2-20), AMP and its analogues HP (2-20), AMP and its analogues Microcin J25, a threaded sidechain-to-backbone ring structure 8-Toxin... 

Figure 16. Isocyanide polymer (R-N=C<)n containing benzo-18-crown-6 sidechains 12. Rigid helices with four repeating units per helical turn arrange the crown ether rings on top of each other and four channel structures are formed. ...

FIGURE 15.6 Structures and names of ligands with P bound to Cp ring and chiral sidechain. 

Further optimization of the P3 substituent revealed that 3,4-bis-alkoxy substitution of the phenyl ring improved potency, with the optimal combination 3-(3-methoxypropoxy) and 4-methoxy (7, Table 2). Compound 7 exhibits exceptional renin inhibitory activity in both buffer and plasma and showed moderate in vivo activity in telemetered, sodium-depleted marmosets, with peak reduction of mean arterial pressure of 9 mm Hg and an 8-h duration of action.20 An X-ray co-crystal structure of compound 7 with recombinant human renin established that the methoxypropoxy sidechain occupies a narrow nonsubstrate pocket, termed S3sp. The importance of terminal methoxy group is... 

More information about the mechanism of the Viscontini reaction has been collected from model studies condensing 4,5,6-triamino-2-methylthiopyrimidine (338) in a similar manner with the phenylhydrazones of l- (339) and D-arabinose and omitting the iodine oxidation step (Scheme 55). Under these conditions an interesting intermediate, consisting of a tricyclic pteridine ring system (341), was formed by intramolecular adduct formation of the trihydroxypropyl sidechain on to the 7-position of the 5,6-hydropteridine precursor (340) (Scheme 55). The main reaction product could be crystallized and the structure unambiguously proven by an x-ray analysis <90HCA808). 

Asphaltene Structure by Spectroscopic Methods. Much of the information available on the carbon skeleton of asphaltenes has been derived from spectroscopic studies of asphaltenes isolated from various petroleums and natural asphalts (I, 2). The data from these studies support the hypothesis that asphaltenes, viewed structurally, are condensed polynuclear aromatic ring systems bearing alkyl sidechains. The number of rings apparently varies from as low as six in smaller systems to fifteen to twenty in more massive systems (13,14). 

Typical Lewis acids such as AlCl3 and ZnCl2 display excellent catalytic activity in most Friedel-Crafts type reactions (9, 10) and are also known to catalyze coal liquefaction and solubilization (11-26). Because of this latter property, acid-catalyzed depolymerization has become a useful method for structural investigation of coal (27). The rationale for solubilization is interpreted either in terms of depolymerization via rupture of the bridges or, since the overall reaction in general is that of Friedel-Crafts alkylation or acetylation, in terms of the effect of the sidechains introduced on the aromatic ring system. 

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