3β-Acetoxy-17-chloro-16-formylandrosta-5,16-diene 2b (130 mg, 0.34 mmol) was added to a suspension of acetamidine hydrochloride (65 mg, 0.69 mmol) and potassium carbonate (190 mg, 1.36 mmol) in DMF (5 mL). The mixture was stirred at 80°C for 6.5 h until the complete conversion of the intermediates (TLC monitoring). The resulting mixture was cooled to room temperature and the solvent was removed under reduced pressure. The crude product was isolated by column chromatography using petroleum ether/ethyl acetate, 1:2, to obtain colorless solid (52 mg, 40% yield). Rf 0.47 (petroleum ether:EtOAc, 1:2; visualized by UV light at 254 nm). The spectral data are consistent with those reported by Gogoi et al. (2013). m.p. 169–171°C [m.p.lit (Gogoi et al., 2013) = 165–167°C]. 1H NMR (600 MHz, DMSO-d6at303K), δ: 0.91 (s, 3H, 18-CH3), 1.05 (s, 3H, 19-CH3), 1.07–1.13 (m, 2H, 1-CH2, 9-CH), 1.49 (dt, J = 4.2, 12.6 Hz, 1H, 12-CH2), 1.53–1.65 (m, 4H, 2-CH2, 11-CH2, 12-CH2, 14-CH), 1.67–1.73 (m, 2H, 7-CH2, 11-CH2), 1.74–1.82 (m, 2H, 2-CH2, 8-CH), 1.86 (dt, J = 3.6, 13.2 Hz, 1H, 1-CH2), 1.99 (s, 3H, CH3CO), 2.05–2.12 (m, 1H, 7-CH2), 2.28–2.32 (m, 2H, 4-CH2), 2.47 (dd, J = 15.0 Hz, 1H, 15-CH2), 2.54 (s, 3H, 2′-CH3), 2.72 (dd, J = 6.6,15.0 Hz, 1H, 15-CH2), 4.43–4.48 (m, 1H, 3-CH), 5.39–5.40 (m, 1H, 6-CH), 8.43 (s, 1H, H-4′). 13C NMR (125 MHz, DMSO-d6at303K), δ: 16.7 (18-CH3), 18.9 (19-CH3), 20.0 (11-CH2), 21.0 (CH3), 25.4 (2′-CH3), 27.3 (2-CH2), 27.3 (15-CH2), 30.1 (8-CH), 30.6 (7-CH2), 32.4 (12-CH2), 36.3 (10-C), 36.3 (1-CH2), 37.7 (4-CH2), 45.4 (13-C), 49.8 (9-CH), 55.0 (14-CH), 73.1 (3-CH), 121.6 (6-CH), 130.5 (16-C), 139.8 (5-C), 151.8 (4′-CH), 165.1 (2′-C), 169.7 (CO), 180.8 (17-C). IR (KBr), cm−1: 2941, 2903, 2858 (CH), 1732 (CO), 1589, 1556 (C = C, C = N). HRMS (ESI) for C24H33N2O2 ([M+H]+): calcd 381.2537, found 381.2535.