Effective formal synthesis of benzomalvin A
1251
5.32 g benzodiazepindione 4 (0.02 mol) in 250 cm3 dry
CH2Cl2 containing 2.63 g triethylamine (0.026 mol) and a
catalytic amount of DMAP. The system was stirred at room
temperature for 3 h, and the reaction mixture was then
concentrated, dissolved in ethyl acetate, and passed
through a short pad of silica gel to furnish the nitro
derivative 5 after drying. The crude residue 5 was dissolved
in 300 cm3 ethyl acetate, and 1.00 g 3% Pd/C was added.
The resulting mixture was stirred under a balloon of
hydrogen gas. After reduction was complete (4 h), as
revealed by TLC monitoring, the reaction mixture was
filtered over a pad of Celite. The filtrate was concentrated
and the residue was purified by silica gel column chroma-
tography using 25–45% ethyl acetate in n-hexane to furnish
4.42 g (60%) 1b; m.p.: 139–140 °C (140–142 °C in [8]).
starting materials. This experimentally simple and envi-
ronmentally friendly approach is now implemented in our
labs to prepare a wide range of benzomalvin A derivatives
for biological evaluation.
Experimental
Melting points were measured using an electrothermal
digital melting point apparatus. IR spectra were recorded
using a Nicolet Impact 410 FT-IR spectrophotometer. Both
1H and 13C NMR spectra were recorded on a Bruker
Avance spectrometer (400 MHz for 1H, 100 MHz for 13C).
The chemical shifts are given on the d scale (ppm) relative
to TMS (used as the internal standard). Mass spectra (MS)
were obtained on an API 3000 LC/MS/MS spectrometer
manufactured by Applied Biosystems MDS Sciex with an
APCI/ESI ion source type used in positive-ion detection
mode. Elemental analysis (C, N, H) was performed on a
CE-440 elemental analyzer, and the results were found to
be in good agreement with calculated values.
Acknowledgments This work was supported by the Deanship of
Research at Jordan University of Science and Technology.
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N-Demethylbenzomalvin A (1b, C23H17O3N2)
A solution of 3.71 g o-nitrobenzoyl chloride (0.02 mol) in
30 cm3 CH2Cl2 was added drop-wise to a solution of
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