New 5-aminopyrazoles 2a-c were prepared in high yields from the reaction of known α,α-dicyanoketene-N,S-acetals 1a-c with hydrazine hydrate under reflux in ethanol. These compounds were utilized as intermediates to synthesize pyrazolo[1,5-a]-pyrimidines 3a-c, 4a-d, 5a-c, and 6a-c, as well as pyrazolo[5,1-c][1,2,4]triazines 7a-c and 8a-c, by the reaction of 2-[bis(methylthio)methylene]malononitrile, α,α-dicyanoketene-N,S-acetals 1a-b, acetylacetone, acetoacetanilide as well as acetylacetone, and malononitrile, respectively. Furthermore, cyclization of 2a-c with pentan-2,5-dione yielded the corresponding 5-pyrrolylpyrazoles 9a-c. Moreover, fusion of 2a-c with acetic anhydride resulted in the corresponding 1-acetyl-1H-pyrazoles 10a-c. The antibacterial activity and cytotoxicity against Vero cells of several selected compounds are also reported.
A new resveratrol dimer, acuminatol (1), was isolated along with five known compounds from the acetone extract of the stem bark of Shorea acuminata. Their structures and stereochemistry were determined by spectroscopic methods, which included the extensive use of 2D NMR techniques. All isolated compounds were evaluated for their antioxidant activity using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity (RSA) and the β-carotene-linoleic acid (BCLA) assays, and compared with those of the standards of ascorbic acid (AscA) and butylated hydroxytoluene (BHT). All compounds tested exhibited good to moderate antioxidant activity in the DPPH assay (IC₅₀s 0.84 to 10.06 mM) and displayed strong inhibition of β-carotene oxidation (IC₅₀s 0.10 to 0.22 mM). The isolated compounds were evaluated on the Vero cell line and were found to be non-cytotoxic with LC₅₀ values between 161 to 830 µM.