Indoloquinoline alkaloids

This reaction has also been applied to the synthesis of indoloquinoline alkaloids (Scheme 10.60).92... 

Fig. 1. HMQC spectrum of a 12 pig (0.05 pmol) sample of the indoloquinoline alkaloid cryptolepine (1) dissolved in 145 pL of d6-DMSO. The data were recorded overnight (16 h) at 500 MHz using a 3 mm micro-inverse-detection NMR probe.6 Both a proton reference spectrum (top trace) and the projection through the Fi frequency domain (bottom trace) are shown above the contour plot. (Reprinted with permission from Ref. 6. Copyright 1992, American Chemical Society and American Society of Pharmacognosy.)...

Fig. 3. Photograph showing 5, 3, and 1.7 mm NMR tubes each containing 1 pmol of the deep violet-colored indoloquinoline alkaloid cryptolepine (3).

Fig. 4. Spectra acquired for a 0.55 pmol sample of the indoloquinoline alkaloid cryptolepine (1) dissolved in 25 pL J6-DMSO. (a) Proton-carbon (HMQC) direct correlation spectrum recorded in 12m (16 x 2048 point files, 16 transients/ increment) shown with no linear prediction, (b) Long-range 1H-13C HMBC spectrum of the same sample optimized for 8 Hz. The data were acquired as 64 x 4096 files with 16 transients accumulated/ increment. Data are again shown without any linear prediction. (Reprinted with permission from Ref. 11. Copyright 1998, John Wiley Sons, Ltd.)...

Later in 1996 the first example of a dimeric indoloquinoline alkaloid, crypt-omisrine (22), was isolated and its structure elucidated.73 Inverse-detected 2D-NMR spectra were recorded using a 3 mm micro-inverse probe 13C chemical shift data were recorded for the sample using a 3 mm micro-dual probe. In addition to the mass spectral data, a 0.9% nuclear overhauser effect (NOE) observed between the HI and H9 protons was used to confirm the structure. 

The simple indoloquinoline alkaloid quindoline (6), which contains two protonated NH resonances, readily afforded H- C and H- N direct heteronuclear shift correlation... 

Another member of the family of Cryptolepus indoloquinoline alkaloids is the dimeric structure cryptomisrine (7). Data used as input for Structure Elucidator v7.0 included and shifts from ID spectra, H- H COSY, HMQC and HMBC,... 

Structure and Solvent Effects on the and Shifts of Indoloquinoline Alkaloids... 

Table 6 Observed, neural network, and DFT-calculated shifts for various indoloquinoline alkaloids [57]... 

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