Naphthoquinone amino acid derivatives, synthesis and biological activity as proteasome inhibitors

Figures & data

Figure 1. (a) Schematic structure of non-peptide inhibitors bearing the 2-cloronaphthoquinonic unit. (b) The general structure of dipeptide derivatives with a 2-chloronaphthoquinone group. (c) The generic structure of the new amino acid derivatives linked to the 2-chloronaphthoquinone group.

Table 1. Inhibition of the proteasome subunits by the synthesised compounds.

Compd	R'	Xaa	R	IC50 (μm)^a T-L	IC50 (μm)^a ChT-L	IC50 (μm)^a PGPH
1	HMB	Leu	–(CH2)2−	77.44 ± 6.51	>100	1.21 ± 0.08
2	NBz	Leu	–(CH2)2−	65.32 ± 5.91	>100	2.35 ± 0.21
3	Bz	Leu	–(CH2)2−	58.43 ± 5.13	>100	2.61 ± 0.23
4	1-NaftCO	Leu	–(CH2)2−	21.08 ± 1.85	0.82 ± 0.08	0.91 ± 0.07
5	HMB	Asn	–(CH2)2−	68.35 ± 5.14	8.47 ± 0.75	6.18 ± 0.55
6	NBz	Asn	–(CH2)2−	17.23 ± 1.09	0.92 ± 0.09	1.19 ± 0.13
7	Bz	Asn	–(CH2)2−	49.66 ± 3.87	7.99 ± 0.67	11.23 ± 0.98
8	1-NaftCO	Asn	–(CH2)2−	35.23 ± 2.77	76.25 ± 6.82	10.01 ± 1.27
9	HMB	Phe	–(CH2)2−	>100	0.85 ± 0.07	0.88 ± 0.08
10	NBz	Phe	–(CH2)2−	35.40 ± 2.91	0.77 ± 0.06	0.24 ± 0.3
11	Bz	Phe	–(CH2)2−	53.18 ± 6.70	6.22 ± 0.48	1.05 ± 0.09
12	1-NaftCO	Phe	–(CH2)2−	49.75 ± 3.97	9.14 ± 1.02	35.76 ± 4.03
13	HMB	Ser	–(CH2)2−	>100	>100	91.52 ± 7.69
14	NBz	Ser	–(CH2)2−	63.36 ± 7.01	83.47 ± 8.03	78.66 ± 8.14
15	Bz	Ser	–(CH2)2−	53.82 ± 4.88	24.11 ± 1.98	5.78 ± 4.35
16	1-NaftCO	Ser	–(CH2)2−	>100	>100	>100
17	HMB	Leu	–(CH2)4−	>100	11.50 ± 1.02	7.82 ± 0.71
18	NBz	Leu	–(CH2)4−	>100	8.40 ± 0.72	10.54 ± 0.82
19	Bz	Leu	–(CH2)4−	>100	10.12 ± 0.70	2.41 ± 0.14
20	1-NaftCO	Leu	–(CH2)4−	>100	49.30 ± 5.02	45.35 ± 4.03
21	HMB	Asn	–(CH2)4−	>100	65.38 ± 6.50	9.52 ± 1.09
22	NBz	Asn	–(CH2)4−	>100	28.52 ± 3.05	>100
23	Bz	Asn	–(CH2)4−	>100	24.19 ± 2.05	>100
24	1-NaftCO	Asn	–(CH2)4−	>100	78.34 ± 6.95	>100
25	HMB	Phe	–(CH2)4−	>100	17.50 ± 1.07	8.82 ± 0.71
26	NBz	Phe	–(CH2)4−	>100	9.10 ± 0.6	10.54 ± 0.82
27	Bz	Phe	–(CH2)4−	>100	10.12 ± 0.70	5.43 ± 0.44
28	1-NaftCO	Phe	–(CH2)4−	79.71 ± 6.97	9.30 ± 1.02	25.65 ± 3.03
29	HMB	Ser	–(CH2)4−	80.24 ± 6.91	45.68 ± 2.59	61.52 ± 4.99
30	NBz	Ser	–(CH2)4−	83.26 ± 7.21	88.74 ± 8.03	83.66 ± 8.16
31	Bz	Ser	–(CH2)4−	>100	84.11 ± 6.08	3.55 ± 1.65
32	1-NaftCO	Ser	–(CH2)4−	60.75 ± 4.88	>100	83.62 ± 5.48
33	HMB	Leu	–cHx-	>100	>100	>100
34	NBz	Leu	–cHx-	>100	42.10 ± 5.02	>100
35	Bz	Leu	–cHx-	>100	23.12 ± 1.70	>100
36	1-NaftCO	Leu	–cHx-	>100	59.30 ± 6.42	73.67 ± 1.45
37	HMB	Asn	–cHx-	>100	>100	>100
38	NBz	Asn	–cHx-	>100	>100	>100
39	Bz	Asn	–cHx-	>100	>100	>100
40	1-NaftCO	Asn	–cHx-	>100	>100	>100
41	HMB	Phe	–cHx-	>100	>100	>100
42	NBz	Phe	–cHx-	>100	82.10 ± 6.52	>100
43	Bz	Phe	–cHx-	>100	73.31 ± 3.90	>100
44	1-NaftCO	Phe	–cHx-	>100	>100	83.37 ± 4.58
45	HMB	Ser	–cHx-	>100	>100	>100
46	NBz	Ser	–cHx-	>100	>100	5.78 ± 0.62
47	Bz	Ser	–cHx-	>100	>100	3.42 ± 0.51
48	1-NaftCO	Ser	–cHx-	>100	>100	11.71 ± 1.25
MG132				1.04 ± 0.092	0.0018 ± 0.00022	>10

^a The values reported are the mean ± SEM of three independent determinations.

Scheme 1. Synthesis of naphthoquinone amino acid derivatives.

Figure 2. Effect of compounds 4, 6, 9–11 on cell proliferation. (a) MDA and (b) A2780 tumour cells cultured for 3 d in the presence or absence of the indicated concentrations of compounds. The means of three independent experiments performed in duplicate are shown.

Figure 3. (a) Molecule 10 in the β1 active site (best pose). (b) Schematic view of the interactions between the receptor and the docked molecule.

Figure 4. (a) Molecule 10 in the β5 active site. (b) Schematic view of the interactions between the receptor and the docked molecule.

Figure 5. Molecule 16 (a), 26 (b) and 42 (c) docked into the ?1 binding site. Molecule 10 docked in the same binding site is reported for comparison.

Figure 6. Molecule 16 (a), 26 (b) and 42 (c) docked into the β5 binding site. Molecule 10 docked in the same binding site is reported for comparison.