Multicomponent synthesis of some new (1S,4S)-2,5-diazabicyclo[2.2.1]heptane-dithiocarbamates and their in vitro anti-proliferative activity against CaSki, MDA-MB-231 and SK-Lu-1 tumour cells as apoptosis inducing agents without necrosis

Figures & data

Figure 1. Structures of some dithiocarbamates and (1S,4S)-2,5-diazabicyclo[2.2.1]heptanes displaying potent anticancer activity.

Scheme 1. Synthesis of (1S,4S)-2-benzyl-2,5-diazabicyclo[2.2.1]heptane dihydrobromide. Reagents and conditions. (a) TsCl, Na₂CO₃, H₂O, 94%; (b) NaBH₄, BF₃–Et₂O, THF, 85%; (c) TsCl, C₅H₅N, toluene, 20 h, 83%; (d) PhCH₂NH₂, toluene, reflux, 96%; (e) HBr 40%, 96%.

Scheme 2. Synthesis of (1S,4S)-tert-butyl 2,5-diazabicyclo[2.2.1]heptane-2-carboxylate.

Scheme 3. One-pot synthesis of (1S,4S)-N-Boc-2,5-diazabicyclo[2.2.1]heptane-dithiocarbamates.

Figure 2. Structures of the synthesized (1S,4S)-N-Boc-2,5-diazabicyclo[2.2.1]heptane-dithiocarbamates.

Figure 3. Antiproliferative dose–response curve of compound 9e on three cancer cell.

Figure 4. Necrotic effect of 9e (at the IC₅₀ values) on both the tumour and lymphocytes cell lines by LDH leakage assay.

Figure 5. Compound 9e induced apoptotic death. Immunodetection of active caspase-3 by compound 9e on CaSki (A), MDA-MB-231 (B) and SK-Lu-1cultures (C).

Figure 6. Effect of the compound 9e on lymphocyte proliferation by CFSE-labelling assay [at the concentrations of 18 (left) and 20 (right) µg mL⁻¹].

Table 1. Experimental data of the compounds 9a–9g.

SL. no	Product	Time (h)	Isolated yield (%)	Melting point	Optical rotation, [α]D^20
1	9a	10	70	109–110 °C	−193.9 (c 1, CH2Cl2)
2	9b	10	68	Viscous liquid	−150.8 (c 1.025, CH2Cl2)
3	9c	11	60	Viscous liquid	−166.84 (c 1.04, CH2Cl2)
4	9d	12	55	228–230 °C	−79.61 (c 0.336, DMSO)
5	9e	10	63	Viscous liquid	−140.4 (c 1.04, CH2Cl2)
6	9f	10	75	98–103 °C	−178.3 (c 178.3, CH2Cl2)
7	9g	10	71	Viscous liquid	−122.7 (c 1.046, CH2Cl2)

Table 2. Spectral data of the compounds 9a–9g.

7	^1H-NMR (300 MHz, CDCl3, ppm): δ = 4.33 (0.5H, s, –CH), 4.21 (0.5H, s, –CH), 3.60 (1H, s, –CH), 3.28–3.22 (1H, m, –CH2), 3.11-3.05 (1H, m, –CH2), 2.97–2.87 (2H, m, –CH2), 2.14 (1H, s, –NH), 1.62-1.56 (2H, m, –CH2), 1.35 (9H, brs, –CH3); ^13C-NMR (75 MHz, CDCl3, ppm): δ = 154.43, 154.16, 79.39, 79.29, 57.16, 56.51, 56.11, 55.98, 52.57, 52.44, 37.03, 36.80, 28.51^20
9a	^1H-NMR (400 MHz, DMSO-d6, ppm): δ = 5.42 (0.5H, s, –CH), 4.99 (0.5H, s, –CH), 4.55–4.29 (1H, m, –CH), 3.74–3.63 (1H, m, –CH2), 3.49–3.40 (1H, m, –CH2), 3.28–3.13 (2H, m, –CH2), 2.58–2.56 (3H, m, –CH3), 2.02–1.75 (2H, m, –CH2), 1.40–1.38 (9H, m, –CH3); ^13C-NMR (100 MHz, DMSO-d6, ppm): δ = 193.36 (C = S), 153.44 (C = O), 64.30, 63.74, 62.52, 62.16, 61.96, 61.40, 58.58, 58.26, 57.33, 57.16, 56.62, 56.36, 56.21, 56.00, 55.70, 54.99, 54.04, 53.63, 53.31, 52.37, 52.10, 51.76, 37.48, 36.94, 36.25, 35.74, 28.11, 28.06, 18.69, 18.56; MS (FAB+): m/z calculated for C12H20N2O2S2 [M + H]^+: 289, found: 289
9b	^1H-NMR (400 MHz, CDCl3, ppm): δ = 7.31–7.16 (5H, m, –ArH), 5.59 (0.5H, s, –CH), 4.89 (0.5H, s, –CH), 4.53–4.43 (3H, m, –CH, –CH2), 3.89–3.31 (4H, m, –CH2), 1.90–1.84 (2H, m, –CH2), 1.39–1.37 (9H, m, –CH3); ^13C-NMR (100 MHz, CDCl3, ppm): δ = 193.78 (C = S), 192.78 (C = S), 154.06 (C = O), 136.14, 129.35, 128.69, 127.62, 80.32, 64.54, 63.89, 62.38, 62.28, 62.18, 61.59, 58.35, 57.55, 56.61, 56.21, 55.23, 52.34, 51.98, 41.25, 41.12, 38.02, 37.55, 36.91, 36.49, 28.50; MS (FAB+): m/z calculated for C18H24N2O2S2 [M + H]^+: 365, found: 365
9c	^1H-NMR (400 MHz, CDCl3, ppm): δ = 8.51 (1H, d, J = 4 Hz, –ArH), 7.60 (1H, td, J = 7.6 Hz, 2 Hz, –ArH), 7.45 (1H, m, –ArH), 7.15–7.12 (1H, m, –ArH), 5.62 (0.5H, s, –CH), 5.01 (0.5H, s, –CH), 4.80–4.47 (3H, m, –CH, –CH2), 3.89–3.37 (4H, m, –CH2), 1.95–1.89 (2H, m, –CH2), 1.42–1.40 (9H, m, –CH3); ^13C-NMR (100 MHz, CDCl3, ppm): δ = 193.56 (C = S), 156.88, 154.11 (C = O), 149.65, 136.83, 123.97, 122.47, 80.44, 64.84, 64.23, 62.62, 62.56, 62.35, 61.78, 58.50, 57.64, 56.70, 56.29, 55.31, 52.41, 52.09, 52.01, 42.63, 38.11, 37.67, 37.01, 36.59, 28.58; MS (FAB+): m/z calculated for C17H23N3O2S2 [M + H]^+: 366, found: 366
9d	^1H-NMR (400 MHz, CDCl3, ppm): δ = 7.52 (2H, brs, –ArH), 7.21–7.19 (2H, m, –ArH), 5.62 (0.5H, s, –CH), 4.95 (0.5H, s, –CH), 4.91–4.50 (3H, m, –CH, –CH2), 3.95–3.31 (4H, m, –CH2), 1.95–1.85 (2H, m, –CH2), 1.44–1.40 (9H, m, –CH3); ^13C-NMR (100 MHz, CDCl3, ppm): δ = 193.61 (C = S), 154.00 (C = O), 151.47, 122.89, 115.56, 80.66, 65.60, 65.00, 63.18, 62.97, 62.37, 58.95, 57.56, 56.67, 56.21, 55.23, 52.32, 51.93, 38.13, 37.69, 37.07, 36.63, 33.30, 33.14, 28.56; MS (FAB+): m/z calculated for C19H24N4O2S2 [M + H]^+: 405, found: 405
9e	^1H-NMR (400 MHz, CDCl3, ppm): δ = 7.31 (1H, s, –ArH), 7.22-7.15 (3H, m, –ArH), 5.59 (0.5H, s, –CH), 4.90 (0.5H, s, –CH), 4.57–4.40 (3H, m, –CH, –CH2), 3.89–3.72 (1H, m, –CH2), 3.63–3.33 (3H, m, –CH2), 1.92–1.85 (2H, m, –CH2), 1.40–1.38 (9H, m, –CH3); ^13C-NMR (100 MHz, CDCl3, ppm): δ = 193.26 (C = S), 192.19 (C = S), 154.13 (C = O), 138.65, 138.60, 134.43, 129.95, 129.41, 127.84, 127.82, 127.58, 80.46, 64.81, 64.16, 62.60, 62.51, 62.32, 61.73, 58.45, 56.66, 56.26, 55.29, 52.41, 52.05, 40.43, 40.29, 38.11, 37.65, 36.98, 36.57, 28.58; MS (FAB+) m/z (%) = 399 [M+], 343, 341, 273, 241, 140, 185, 141, 125, 57; MS (FAB+): m/z calculated for C18H23ClN2O2S2 [M + H]^+: 399, found: 399
9f	^1H-NMR (400 MHz, DMSO-d6, ppm): δ = 7.45–7.41 (2H, m, –ArH), 7.17–7.10 (2H, m, –ArH), 5.43 (0.5H, s, –CH), 5.00 (0.5H, s, –CH), 4.60–4.29 (3H, m, –CH, –CH2), 3.78–3.65 (1H, m, –CH2), 3.48–3.37 (1H, m, –CH2), 3.34–3.12 (2H, m, –CH2), 2.00–1.75 (2H, m, –CH2), 1.40–1.38 (9H, m, –CH3); ^13C-NMR (100 MHz, DMSO-d6, ppm): δ = 191.66 (C = S), 162.59, 160.17, 153.36 (C = O), 132.82, 131.09, 131.01, 115.31, 115.10, 79.25, 79.13, 64.45, 63.88, 62.60, 62.25, 62.12, 61.54, 58.58, 58.31, 57.27, 56.31, 55.92, 54.92, 52.38, 52.05, 51.66, 38.86, 37.42, 36.90, 36.16, 35.65, 28.07, 28.01; MS (FAB+): m/z calculated for C18H23FN2O2S2 [M + H]^+: 383, found: 383
9g	^1H-NMR (400 MHz, CDCl3, ppm): δ = 7.45–7.24 (5H, m, –ArH), 5.65–5.61 (0.3H, m), 5.39 (0.24H, d, J = 8 Hz), 5.02–4.97 (0.8H, m), 4.70–4.35 (1H, m), 4.15–3.27 (7H, m), 1.98–1.73 (2H, m, –CH2), 1.43–1.38 (9H, m, –CH3); ^13C-NMR (100 MHz, CDCl3, ppm): δ = 193.18 (C = S), 154.10 (C = O), 143.03, 129.06, 128.97, 128.74, 128.66, 128.27, 128.15, 128.01, 127.98, 126.00, 125.97, 80.54, 73.48, 66.52, 66.27, 65.99, 65.04, 64.96, 64.84, 64.39, 62.70, 62.54, 61.95, 58.78, 58.67, 58.55, 57.60, 57.12, 56.97, 56.66, 56.30, 55.33, 55.26, 54.17, 53.74, 53.58, 52.35, 52.09, 51.99, 45.12, 44.93, 44.77, 44.63, 38.09, 37.64, 37.02, 36.62, 28.60; MS (FAB+): m/z calculated for C19H26N2O3S2 [M + H]^+: 395, found: 395

Table 3. Antiproliferative activities of the synthesized (1S,4S)-N-Boc-2,5-diazabicyclo[2.2.1]heptane-dithiocarbamates (9a–9g).

Compound	IC50 (µg mL^−1)
	CaSki	MDA-MB231	SK-Lu-1
9a	346	150	300
9b	294	69	57
9c	305	100	120
9d	214	100	87
9e	28	18	20
9f	348	227	237
9g	137	50	40
Cisplatin^a	1.67	2.37	1.36

All the experimental results are the average of three independent experiments.

^a The assay was performed with a commercially available sample of Cisplatin, purchased from Sigma-Aldrich.

Table 4. In silico prediction of physicochemical pharmacokinetic properties²⁴.

Code	miLogP^a	nON^b	nOHNH^c	n-Violations^d	Nrotb^e	MW^f
Rule	≤5	<10	<5	≤1	–	<500
9e	4.55	4	0	0	6	342.47

^a miLogP: logarithm of partition coefficient of compound between n-octanol and water.

^b n-ON acceptors: number of hydrogen bond acceptors.

^c n-OHNH donors: number of hydrogen bonds donors.

^d n-violations: number of violations according to Lipinski’s rule.

^e Nrotb: number of rotatable bonds.

^f MW: molecular weight.

Beinat C, Banister SD, McErlean CSP, et al. Practical synthesis of (1S,4S)-2,5-diazabicyclo[2.2.1]heptane. Tetrahedron Lett 2013;54:5345–7.

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Molinspiration Cheminformatics, Bratislava, Slovak Republic. Available from: http://www.molinspiration.com/cgi-bin/properties [last accessed 26 Jul 2016].

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