Development of terphenyl-2-methyloxazol-5(4H)-one derivatives as selective reversible MAGL inhibitors

Figures & data

Figure 1. Structures of some of the most relevant MAGL inhibitors.

Figure 2. Structural evolution of methyleneoxazol-5(4H)-one scaffold: previously developed biphenyl 2-methyloxazol-5(4H)-one compounds (A) and newly synthesised terphenyl-2-methyloxazol-5(4H)-one derivatives (B).

Scheme 1. Reagents and conditions: (a) for compound 4: phenylboronic acid, Pd(OAc)₂, K₃PO₄, TBAB, H₂O, 125 °C; for compound 6: phenylboronic acid, Pd(OAc)₂, PPh₃, aq. 2 M Na₂CO₃, toluene, EtOH, 100 °C; for compound 8: phenylboronic acid, Pd(OAc)₂, PPh₃, aq. 2 M Na₂CO₃, toluene, EtOH, 100 °C, then phenylboronic acid, Pd₂(dba)₃, Cs₂CO₃, Cy₃P 20% toluene, dioxane, 100 °C; (b) N-acetylglycine, Ac₂O, CH₃COONa, reflux.

Scheme 2. Reagents and conditions: (a) phenylboronic acid, Pd(OAc)₂, PPh₃, aq. 2 M Na₂CO₃, toluene, EtOH, 100 °C; (b) N-acetylglycine, Ac₂O, CH₃COONa, reflux.

Scheme 3. Reagents and conditions: (a) phenylboronic acid, Pd₂(dba)₃, Cs₂CO₃, Cy₃P 20% toluene, dioxane, 100 °C; b) N-acetylglycine, Ac₂O, CH₃COONa, reflux.

Scheme 4. Reagents and conditions: (a) variously substituted phenylboronic acid, Pd(OAc)₂, PPh₃, aq. 2 M Na₂CO₃, toluene, EtOH, 100 °C; (b) N-acetylglycine, Ac₂O, CH₃COONa, reflux.

Table 1. Experimental inhibition activity (IC₅₀) on human MAGL and FAAH of the analyzed compounds.

#	Ar1	Ar2	Ar3	Ar4	MAGL IC50 (nM)	FAAH IC50 (nM)	MAGL/FAAH selectivity
5	H	Ph	Ph	H	837 ± 18	2321 ± 51	3
7	Ph	H	Ph	H	546 ± 20	18161 ± 904	33
9	Ph	Ph	H	H	2558 ± 172	20055 ± 1438	8
13	H	Ph	H	Ph	457 ± 10	14763 ± 1176	32
15	Ph	H	H	Ph	320 ± 10	10860 ± 161	34
#	R1		R2		MAGL IC50 (nM)	FAAH IC50 (nM)	MAGL/FAAH selectivity
20a	F		H		683 ± 50	27989 ± 1306	41
20b	OCH3		H		348 ± 38	36118 ± 1123	104
20c	OCF3		H		4194 ± 299	17728 ± 1198	4
20d	CF3		H		6763 ± 1125	28992 ± 1157	4
20e	H		F		628 ± 32	11713 ± 895	19
20f	–OCH2O–				673 ± 23	23712 ± 1348	35
20g	OCH3		F		335 ± 2	22311 ± 1239	67
20h	Cl		H		476 ± 39	11487 ± 998	24
CAY10499					144 ± 4	14.7 ± 0.2	0.1
JZL-184					49.8 ± 4.2	3301 ± 205	66

Figure 3. Compound 20b-MAGL inhibition analysis. (A) IC₅₀ (µM) values of 20b at different preincubation times with hMAGL (0, 30 and 60 min). (B) Dilution assay: the first two columns indicate the inhibition percentage of compound 20b at a concentration of 10 and 0.25 µM. The third column indicates the inhibition percentage of compound 20b after dilution (final concentration = 0.25 µM).

Figure 4. Minimised average structure of compound 20b docked into MAGL receptor (A) and analysis of 20b-MAGL H-bond interactions (B). The plot shows the distance analysis for the two H-bonds (i.e. HB1 and HB2).

Figure 5. Minimised average structure of compound 20b docked into FAAH receptor.

Table 2. MM-PBSA results for compound 20b docked into MAGL and FAAH.

Protein	Ele	VdW	PBsur	PB	ΔPBSA
MAGL	−12.5	−52.2	43.4	−5.2	−26.5
FAAH	−3.2	−50.1	40.2	−5.3	−18.5

ΔPBSA is the sum of the electrostatic (Ele), van derWaals (VdW), polar (PB) and non-polar (PBSur) solvation free energy. Data are expressed as kcal•mol⁻¹.