Synthesis and biological activity of pyrazolo[3,4-d]thiazolo[3,2-a]pyrimidin-4-one derivatives: in silico approach

Figures & data

Table 1.  Structure of pyrazolopyrimidine derivatives.

Entry	Substitutent				Yield (%)	M.P. (°C)
	R1	R2	R3	R4
3a	H	H	Cl	H	65	204
3b	OH	H	H	H	66	215
3c	OH	H	H	Cl	64	220
3d	OH	Br	H	Cl	65	195
3e	H	H	NO2	H	66	202
3f	H	H	Br	H	66	202
3g	OH	H	Cl	CH3	68	220
3h	OH	H	Cl	Cl	68	192
3i	H	H	OH	H	67	241
3j	OH	I	H	Cl	68	210

Scheme 1.  Synthesis of pyrazolopyrimidine derivatives.

Table 2.  Ki and IC₅₀ values of the inhibitors.

Sr. no.	Inhibitor	Type of inhibition	Ki value (μg/mL)	IC50 value (μg)	% Inhibition
1	3-Amino-6-(2-hydroxy phenyl)-1H-pyrazolo[3,4-d]thiazolo[3,2-a]pyrimidin-4-one (3b)	Competitive	3.56	4.228	59
2	3-Amino-6-(2-hydroxy-4-chloro-5-methylphenyl)-1H-pyrazolo[3,4-d]thiazolo[3,2-a]pyrimidin-4-one (3g)	Competitive	2.337	3.1	58
3	Allopurinol	Competitive	1.816	2.9	66

Table 3.  Physicochemical properties and docking values of pyrazolo[3,4-d]thiazolo[3,2-a]pyrimidin-4-one derivatives.

Compound	Functional groups	Molecular formula	Molecular weight	Log P	Solubility	Mutagenicity	HBD	HBA	Pa	Dock score	Drug score
3a	Cl	C13H10ClN5OS	319	0.75	−3.86	Non-mutagenic	3	4	0.404	−83.2	0.83
3b	OH,	C13H11N5O2S	301.06	−0.16	−2.82	Non-mutagenic	4	5	0.329	−85	0.9
3c	OH, Cl	C13H10ClN5O2S	335.02	0.45	−3.56	Non-mutagenic	4	5	0.358	−80.4	0.84
3d	Br,OH, Cl	C13H9BrClN5O2S	413	1.15	−4.39	Non-mutagenic	4	5	0.356	−80	0.68
3e	NO2	C13H12N6O3S	332.07	−0.43	−3.46	Slightly mutagenic	5	6	0.346	−85.4	0.83
3f	Br	C13H10BrN5OS	362.98	0.54	−3.66	Non-mutagenic	3	4	0.316	−78.3	0.78
3g	OH,Cl, CH3	C14H12ClN5O2S	349	0.77	−3.9	Non-mutagenic	4	5	0.356	−90.9	0.79
3h	OH,Cl, Cl	C13H9Cl2N5O2S	369	1.06	−4.3	Non-mutagenic	4	5	0.359	−85.6	0.74
3i	OH	C13H11N5O2S	301.06	−0.16	−2.82	Non-mutagenic	4	5	0.329	−87.3	0.54
3j	OH, I, Cl	C13H9ClIN5O2S	461	1.38	−4.58	Non-mutagenic	4	5	0.321	−86.4	0.64
Allopurinol	—	C5H4N4O	136.04	−2.78	−1.54	Non-mutagenic	2	3	0.8	−55	0.95
Febuxostat	—	C16H16N2O3S	316.09	2.96	−2.63	Non-mutagenic	1	6	0.782	−96	0.67

Figure 1.  Lineweaver–Burk plot showing competitive inhibition of XO by derivative 3b with varying concentration of xanthine (1–5 µg/mL) and fixed concentration of enzyme (0.0405 U/mL) in potassium phosphate buffer (50 mM, pH 7.4) to a total reaction volume of 3.5 mL.

Figure 2.  Lineweaver–Burk plot showing competitive inhibition of XO by derivative 3g with varying concentration of xanthine (1–5 µg/mL) and fixed concentration of enzyme (0.0405 U/mL) in potassium phosphate buffer (50 mM, pH 7.4) to a total reaction volume of 3.5 mL.

Figure 3.  Lineweaver–Burk plot showing competitive inhibition of XO by allopurinol with varying concentration of xanthine (1–5 µg/mL) and fixed concentration of enzyme (0.0405 U/mL) in potassium phosphate buffer (50 mM, pH 7.4) to a total reaction volume of 3.5 mL.