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Chapter 4
Synthesis of highly substituted pyrazolopyrimidine
Song Qing Wang et al. 21 have been designed some new 5-methyl-7-
substituted–pyrazolo[1,5-a]pyrimidine-3-carbonitrile derivatives on the basis of the
Zaleplon structure for studies on their hypnotic activity. The preliminary
pharmacological evaluations indicated that some compounds showed hypnotic
activity, among that one compound (Figure-6) was the most potent one.
Figure-6
Robert H. Springer et al. 22 has prepared a number of 3,7-disubstituted 6-
carbethoxypyrazolo[ 1,5-a]pyrimidines and 3,7-disubstituted 6-ethoxypyrazolo-[1,5-
a]pyrimidines (Figure-7) have been and evaluated as adenosine cyclic 3’,5’-
phosphate (cAMP) phosphodiesterase (PDE) inhibitors vs. the low K, enzyme isolated
from beef heart, rabbit lung, and kidney preparations. The results were found to be
between 0.5 to 13 times as potent as theophylline as inhibitors of PDE, depending on
the tissue source. A number of these PDE inhibitors exhibited significant
physiological effects in different animal systems, suggesting it should be possible to
obtain selective PDE inhibition in various tissues. Several of these heterocycles were
found superior to adenosine in inhibiting ADP-induced platelet aggregation in vitro.
N
R 1
N
R 1
O
R 2
N
N
R 1 =H, C 2 H 5 ,NO 2 , Br, COOEt
R 2 =OH, NH 2 ,OC 2 H 5 ,SH,SC 2 H 5
Figure-7
Robin R. Frey et al. 23 have discovered 7-aminopyrazolo[1,5-a]pyrimidine urea
receptor tyrosine kinase inhibitors. Investigation of structure-activity relationships of
the pyrazolo[1,5-a]pyrimidine nucleus led to a series of 6-(4-N,N′-diphenyl)ureas that
potently inhibited a panel of vascular endothelial growth factor receptor (VEGFR)
and platelet-derived growth factor receptor (PDGFR) kinases. Several of these
compounds are potent inhibitors of kinase insert domain-containing receptor tyrosine
kinase (KDR) both enzymatically(