C ring substitutions

In 1990, Lange et al. isolated 7-methoxymurrayacine (125) from the roots of M. siamensis (57). The UV and IR spectra of 7-methoxymurrayacine (125) were very similar to those of murrayacine (124) indicating a 3-formylcarbazole. The H-NMR spectrum of 7-methoxymurrayacine also resembled that of murrayacine. However, the C-ring substitution pattern was similar to that of murrayamine-A (120) (see Scheme 2.22), indicating the presence of a substituent at C-7. This regiochemical assignment was supported by the H-NMR spectrum which showed an ortho-coupled (7=8.4 Hz) H-5 at 7.84, an ortho- and mete-coupled (/=8.4, 2.2 Hz) H-6 at 5 6.86, and a mete-coupled (/=2.2 Hz) H-8 at S 6.90. These spectroscopic data led to structure 125 for 7-methoxymurrayacine. 

Wang and coworkers have explored and extended the utility of halogenations of indoles by Cu(II)Cl2 and Cu(II)Br2 [50]. The best results were obtained in dichloro-methane or acetonitrile in the presence of NaOH and silica gel. Similar conditions were successfully applied to C-ring substituted 1-methylindoles. When the reaction mixture included water and fefra-butylammonium bromide, the 2,3-dibromo products were formed. 1,3-Dimethylindole gave a good yield of the 2-bromo product under the latter conditions. 1-Unsubstituted indoles often present problems, but by using NaOH/sihca and CuCU, 2-chlorination of 3-methylindole was achieved in 86% yield. 

C-Ring substituted indoles, including 4-nitroindole, are also allylated under these conditions. The reaction is believed to proceed by an Sa I mechanism, with the Zn(03SCF3)2 acting as a Lewis acid catalyst. There may also be some N-H deprotonation by the amine. 1-Methylindole reacts under these conditions, but with reduced yield. The Zn(03SCF3)2-mediated reaction was used in tandem with intramolecular nucleophilic capture to synthesize the flustramine structure [89]. 

Figure 7.1. Molecular structures of (a) metallophthalocyanine (MPC), (b) metallopor-phyrin (MP), and (c) ring substituted MPc where R = (CH2)2N b(R)xI -...

Confirms cholanoic acid (C24) structure Confirms homocholanoic acid (C25) structure Characteristic loss in 3P-hydroxy-A structures Characteristic of 12-oxo cholanoates Indicates cholestanoic side chain with A bond or -OTMS Confirms cholestanoic acid (C27) structure Characteristic of C29-dicarboxyhc side chain structure Establishes C-ring substitution Observed in C-24 hydroxy cholestanoic acids... 

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