Microwave-assisted synthesis, anti-inflammatory and anti-proliferative activities of new maslinic acid derivatives bearing 1,5- and 1,4-disubstituted triazoles

Figures & data

Figure 1. Chemical structure of Maslinic acid 1.

Table 1. Method I and II for the synthesis of dipolarophiles 2–6^a.

Compounds	Method I (82%)^b	(%)^c	Method II (99%)^b	(%)^c
2		44		25
3	NaH (2 equiv)^d	5	NaH (4 equiv)^d	0
4	propargyl bromide	15	propargyl bromide	23
5	(3 equiv)^d	11	(4 equiv)^d	20
6	2 h	7	8 h	31

^aMaslinic acid (1) in dry DMF as solvent at room temperature.

^b yield of mixture, based on the starting material (compound 1).

^c Isolated yield of compounds (2–6) after column chromatography (EP-EtOAc), based on the maslinicacid (1).

^d Referred to the starting material (compound 1).

Table 2. Optimization of the 1,3-dipolar cyclization for the ruthenium-catalyzed click reaction^a.

Entry	Mol% of Ru(II)^b	Method	Time (h)	Yield (%)
1	2	110 °C (Toluene)	8	55
2	5	110 °C (Toluene)	8	82
3	10	110 °C (Toluene)	8	78
4	5	rt (Toluene)	48	30
5	5	MW^c (DMF)	0.1	98
6	5	MW^c (H2O)	0.4	Traces
7	5	MW^c (DMF/H2O (2:1))	0.1	86
8	5	MW^c (Solvent free)	0.4	No reaction

Bold in entry highlight the optimal reaction condition.

^a Alkyne 2 (2  mmol) and two equivalents of phenylazide (7a).

^b Referred to the starting alkyne 2.

^c The reaction was performed at 250 W.

Scheme 1. Synthesis of the 1,5- and 1,4-triazolyl (8a–g, 9a–g) derivatives. Reagents and conditions: (a) [Cp*RuCl(PPh₃)₂], DMF, Microwave (250 W, 4–8 min), 83–98%. (b) Cuprous iodide (CuI), Et₃N, solvent free, Microwave (200 W, 2–4 min), 90–99%.

Table 3. Maslinic acid-1,5- and 1,4-disubstituted triazolyl derivatives varying at aromatic ring.

		1,5-Regioisomers (RuAAC)		1,4-Regioisomers (CuAAC)
Entry	R	Time (min)	Yield% (Compounds)	Time (min)	Yield% (Compounds)
1		6	98 (8a)	2	99 (9a)
2		4	98 (8b)	2	98 (9b)
3		6	95 (8c)	4	94 (9c)
4		4	96 (8d)	4	94 (9d)
5		8	83 (8e)	4	90 (9e)
6		6	95 (8f)	2	96 (9f)
7		6	96 (8g)	2	95 (9g)

Table 4. Optimization of CuAAC under microwave conditions for 9a^a.

			Irradiation time^c
Entry	Catalyst loading CuI (equiv)^b	Solvent	2 min	5 min	15 min
1	0.1	DMF	–	–	45%
2	0.3	DMF	–	78%	80%
3	0.5	DMF	92%	100%	–
4	0.5	H2O	–	–	70%
5	0.5	Solvent free	100%	–	–

^a Maslinic acid-alkyne 2 (2  mmol), Et₃N (2  mmol) and two equivalents of phenylazide (7a).

^b Referred to the starting alkyne 2.

^c The reaction was performed at 200 W.

Scheme 2. Bis-1,4-disubstituted triazoles 10a–g and 11a–g prepared by the Cu(I)-catalyzed synthesis.

Table 5. Optimization of CuAAC under microwave and solvent free conditions for 10a^a.

	Irradiation timec (min)
Catalyst loading CuI (equiv)^b	4	6	12
0.5	–	–	55%
0.6	–	–	80%
0.7	85%	100%	–
0.8	100%	–	–

^aMaslinic acid-bis-alkyne 4 (2  mmol), Et₃N (4  mmol) and 4 equivalents of phenylazide (7a).

^b Referred to the starting bis-alkyne 4.

^c The reaction was performed at 250 W.

Scheme 3. Tri-1,4-disubstituted triazoles 12a–g prepared by the Cu(I)-catalyzed synthesis.

Table 6. Effect of natural pentacyclic triterpenoid (Maslinic acid 1) and the synthesized triazoles on viability and inflammatory cytokine (IL-1β) production in LPS-stimulated PBMCs.

		Conc. (μM)	% PBMCs viability (/Control)	% IL-1β production (/Control)
DMSO 0.33% + LPS (Control)			100 ± 4	100 ± 2
ZVAD + LPS		5	110 ± 4	42 ± 2
DEXA + LPS		1	81 ± 7	32 ± 2
PRED + LPS		70	67 ± 8	43 ± 4
Entry	Code
1	1	100	14 ± 7	Nd
		30	53 ± 5	109 ± 3
Mono-1,5-disubstituted triazoles
2	8b	100	87 ± 4	91 ± 3
		30	93 ± 5	Nd
3	8c	100	76 ± 3	60 ± 2
		30	74 ± 5	Nd
4	8d	100	94 ± 3	61 ± 5
		30	87 ± 4	Nd
5	8e	100	75 ± 4	42 ± 1
		30	93 ± 3	Nd
6	8f	100	51 ± 7	46 ± 3
		30	99 ± 9	Nd
7	8g	100	93 ± 2	76 ± 1
		30	95 ± 7	Nd
Mono-1,4-disubstituted triazoles
8	9a	100	92 ± 6	62 ± 1
		30	91 ± 6	Nd
9	9b	100	71 ± 5	65 ± 2
		30	75 ± 9	Nd
10	9c	100	83 ± 4	82 ± 4
		30	55 ± 1	Nd
11	9d	100	92 ± 8	21 ± 1
		30	74 ± 2	Nd
12	9f	100	88 ± 10	59 ± 3
		30	97 ± 3	Nd
13	9g	100	97 ± 2	53 ± 3
		30	88 ± 7	Nd
Bis-1,4-disubstituted triazoles
14	10a	100	92 ± 5	71 ± 2
		30	92 ± 3	Nd
15	10c	100	98 ± 4	56 ± 2
		30	94 ± 2	Nd
16	10f	100	66 ± 2	100 ± 4
		30	93 ± 5	Nd
17	10g	100	97 ± 3	95 ± 2
		30	80 ± 5	Nd
18	11a	100	88 ± 5	82 ± 1
		30	82 ± 4	Nd
19	11b	100	74 ± 5	34 ± 2
		30	88 ± 2	Nd
20	11c	100	71 ± 2	74 ± 2
		30	91 ± 5	Nd
21	11f	100	81 ± 5	52 ± 1
		30	83 ± 5	Nd
22	11g	100	95 ± 5	91 ± 3
		30	93 ± 5	Nd
Tri-1,4-disubstituted triazoles
23	12b	100	73 ± 1	43 ± 3
		30	96 ± 2	Nd
24	12c	100	83 ± 5	47 ± 2
		30	85 ± 3	Nd
25	12f	100	40 ± 5	Nd
		30	63 ± 4	23 ± 3
26	12g	100	31 ± 1	Nd
		30	72 ± 5	34 ± 3

Table 7. Effect of natural pentacyclic triterpenoid 1 and the synthesized triazoles on viability of EMT-6 and SW480 cell lines.

			Viability (%/Control)
Tissue:			Breast	Colon
Cell line:		Conc. (μM)	EMT-6	SW480
DMSO 0.33% (Control)			14 ± 2	100 ± 2
Doxorubicin		10	6 ± 0	25 ± 1
Etoposide		10	41 ± 2	70 ± 5
5-fluorouracil		10	26 ± 1	92 ± 2
Methotrexate		10	14 ± 2	68 ± 0
Entry	Code
1	1	100	5 ± 0	9 ± 0
		30	5 ± 0	11 ± 1
		10	100 ± 2	123 ± 2
1,5-disubstituted triazoles
2	8b	100	103 ± 1	122 ± 1
		30	97 ± 0	108 ± 1
		10	96 ± 2	106 ± 6
3	8c	100	24 ± 0	51 ± 1
		30	54 ± 0	61 ± 3
		10	96 ± 1	75 ± 0
4	8d	100	13 ± 1	34 ± 11
		30	108 ± 2	128 ± 3
		10	105 ± 2	118 ± 4
5	8e	100	40 ± 0	99 ± 2
		30	110 ± 3	117 ± 2
		10	108 ± 1	110 ± 0
6	8f	100	43 ± 1	56 ± 3
		30	62 ± 2	73 ± 3
		10	104 ± 3	108 ± 0
7	8g	100	47 ± 4	59 ± 1
		30	102 ± 0	99 ± 0
		10	110 ± 0	120 ± 0
Mono-1,4-disubstituted triazoles
9	9a	100	15 ± 1	45 ± 1
		30	33 ± 1	74 ± 0
		10	92 ± 3	102 ± 1
10	9b	100	40 ± 0	59 ± 3
		30	66 ± 1	86 ± 9
		10	109 ± 0	96 ± 5
11	9c	100	9 ± 0	13 ± 0
		30	6 ± 0	10 ± 0
		10	87 ± 1	19 ± 2
12	9d	100	7 ± 0	13 ± 0
		30	92 ± 0	113 ± 9
		10	108 ± 0	112 ± 11
13	9f	100	39 ± 3	64 ± 2
		30	70 ± 0	77 ± 1
		10	98 ± 0	94 ± 4
14	9g	100	76 ± 4	73 ± 0
		30	87 ± 0	87 ± 0
		10	102 ± 3	93 ± 3
Bis-1,4-disubstituted triazoles
15	10a	100	116 ± 0	103 ± 1
		30	114 ± 0	114 ± 1
		10	113 ± 1	119 ± 0
16	10c	100	118 ± 0	117 ± 0
		30	115 ± 0	115 ± 1
		10	111 ± 4	117 ± 1
17	10f	100	123 ± 0	112 ± 1
		30	117 ± 1	112 ± 2
		10	113 ± 1	111 ± 1
18	10g	100	117 ± 1	116 ± 4
		30	111 ± 2	111 ± 3
		10	112 ± 2	115 ± 1
19	11a	100	115 ± 1	103 ± 1
		30	110 ± 0	100 ± 1
		10	109 ± 1	102 ± 0
20	11b	100	108 ± 0	108 ± 0
		30	108 ± 1	107 ± 1
		10	109 ± 0	105 ± 3
21	11c	100	105 ± 0	116 ± 1
		30	108 ± 2	122 ± 3
		10	110 ± 1	115 ± 8
22	11f	100	104 ± 1	115 ± 1
		30	105 ± 1	109 ± 1
		10	106 ± 0	106 ± 4
Tri-1,4-disubstituted triazoles
24	12b	100	100 ± 4	119 ± 3
		30	100 ± 2	113 ± 4
		10	107 ± 2	107 ± 6
25	12c	100	46 ± 0	123 ± 6
		30	63 ± 6	123 ± 8
		10	100 ± 3	114 ± 4
26	12f	100	8 ± 0	13 ± 0
		30	40 ± 1	70 ± 3
		10	109 ± 1	116 ± 2
27	12g	100	8 ± 0	13 ± 0
		30	90 ± 1	98 ± 4
		10	110 ± 1	111 ± 0