Reaction Steps
A cold (10°-12° C.) mixture of 3-(5-nitro-3-indolyl)-1-propanol (Example 3: 2.2 g, 10.0 mmol), ethanethiol (7.4 ml, 0.1 mol) and Zn dust (2.0 g, 30.6 mmol) in dry DMF (20 ml) kept under argon was treated portionwise with NH4Cl which was added at 10 min interval for 3 h while temperature of the mixture was kept between 10°-12° C. After the addition was completed, the reaction mixture was stirred for 3 h and then diluted with THF:EtOAc (1:2, 45 ml) mixture followed by slow addition of water (40 ml). The mixture was filtered on a glass fiber filter and the two phases separated. The aqueous phase was extracted with EtOAc: THF (2:1, 3×40 ml) mixture The organic extracts were combined, washed with water (2×50 ml), dried (MgSO4) and concentrated in vacuo. The crude material was chromatographed on silica gel dry column using first a mixture of CH2Cl2 : EtOAc (3:17) and then EtOAc both containing Et3N (0.5%). Appropriate fractions were concentrated in vacuo affording 3-(5-amino-4-ethylthio-3-indolyl)-1-propanol (0.50 g, 20%); 1H NMR (DMSO-d6) δ (ppm): 10.48 (s, 1H, indolic NH), 7.08 (d, J=8.5 Hz, 1H, indolic H-7), 6.94 (d, J=2.3 Hz, 1H, indolic H-2), 6.59 (d, J=8.5 Hz, indolic H-6), 4.88 (bs, 2H, NH2), 4.37 (t, J=5.1 Hz, 1H, OH), 3.4-3.6 (m, 2H, H-1), 2.9-3.1 (m, 2H, H-3), 2.65 (q, J=7.4 Hz, 2H, SCH2CH3), 1.7-1.9 (m, 2H, H-2), 1.09 (t, J=7.4 Hz, 3H, SCH2CH3); also isolated was 3-(5-amino-3-indolyl)-1-propanol (1.0 g, 55%); 1H NMR (DMSO-d6) δ (ppm): 10.2 (s, 1H, indolic NH), 7.00 (d, J=8.4 Hz, 1H, indolic H-7), 6.88 (dd, J=2.2 Hz, indolic H-2), 6.63 (d, J=2.0 Hz, indolic H-4), 6.44 (dd, J=8.4 Hz, J=2.0 Hz, 1H, indolic H-6), 4.4-4.6 (m, 3H, NH2 and OH), 3.3-3.5 (m, 2H, H-1), 2.5-2.7 (m, 2H, H-3), 1.6-1.9 (m, 2H, H-2).
