Isocoumarins: a new class of selective carbonic anhydrase IX and XII inhibitors

Figures & data

Figure 1. Coumarin (A) and isocoumarin (B), and their hydrolysis prroducts (C–E).

Scheme 1. General synthetic route for the synthesis of the isocoumarin-substituted compounds X(1-20). Reagent and conditions: (i) chloroacetone, TEA, 170 °C, (ii) substituted phenylhydrazine hydrochloride, EtOH, sodium acetate, 2 h reflux, (iii) DMF/POCl₃, 0–5 °C, then 3 h reflux, (iv) barbituric acid/2-thiobarbituric acid, acetic acid.

Table 1. Inhibition data of human CA I, II, IX and XII with compounds X1-20 and the standard sulphonamide inhibitor acetazolamide (AAZ) by a stopped-flow CO₂ hydrase assay⁷.

Cmpd.	R1	R2	X	KI (µM)^a^,b
				hCA I	hCA II	hCA IX	hCA XII
X1	-H	-H	–	>100	>100	4.3	1.9
X2	-H	-Cl	–	>100	>100	3.5	4.6
X3	-H	-CN	–	>100	>100	2.8	1.2
X4	-CH3	-H	–	>100	>100	3.9	2.3
X5	-CH3	-Cl	–	>100	>100	2.7	5.8
X6	-H	-H	–	>100	>100	7.1	6.5
X7	-H	-Cl	–	>100	>100	6.2	11.6
X8	-H	-CN	–	>100	>100	8.0	8.3
X9	-CH3	-H	–	>100	>100	8.9	8.1
X10	-CH3	-Cl	–	>100	>100	8.1	13.4
X11	-H	-H	O	>100	>100	46.2	41.7
X12	-H	-Cl	O	>100	>100	>100	>100
X13	-H	-CN	O	>100	>100	62.4	36.2
X14	-CH3	-H	O	>100	>100	54.6	66.5
X15	-CH3	-Cl	O	>100	>100	>100	>100
X16	-H	-H	S	>100	>100	49.7	47.1
X17	-H	-Cl	S	>100	>100	>100	>100
X18	-H	-CN	S	>100	>100	78.9	53.4
X19	-CH3	-H	S	>100	>100	72.3	62.8
X20	-CH3	-Cl	S	>100	>100	>100	>100
AAZ	–	–	–	0.250	0.0125	0.026	0.0057

^aMean from three different assays, by a stopped flow technique (errors were in the range of ± 5–10% of the reported values).

^bincubation time 6 h.

Khalifah RG. The carbon dioxide hydration activity of carbonic anhydrase. I. Stop-flow kinetic studies on the native human isoenzymes B and C. J Biol Chem 1971;246:2561–73.

 PubMed Web of Science ®Google Scholar