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.

New α-cyanoketene-N,S-acetals 2(a–g) and β-dialkylamine-α-cyanoacrylates 3(g–i) were synthesized in good to excellent yields by the reaction of ethyl 2-cyano-3,3-bis(methylthio)acrylate 1 with secondary aliphatic amines (i.e., N-methylalkyl- and N-ethylalkylamines), and pyrrolidine, in the presence of triethylamine, under reflux in ethanol, for 1–16 h, depending on the amine used. Five N-methylalkyl amines and pyrrolidine yielded exclusively mono-substituted N,S-acetals 2(a–f) in good yields. On the other hand, N-ethylbenzylamine gave a mixture of monosubstituted products including N,S-acetal 2g in 35% yield and the unexpected product ethyl 3-[benzyl(ethyl)amino]-2-cyanoacrylate 3g in 50% yield. N-Ethylcyclohexylamine and N-ethylbutylamine did not produce N,S-acetals and gave only the unexpected products ethyl 2-cyano-3-[cyclohexyl(ethyl)amino]acrylate 3h and ethyl 3-[butyl(ethyl)amino]-2-cyanoacrylate 3i in good yields. The α-cyanoketene-N,S-acetals 2(a–f), 2j, and 2k underwent cyclization with the binucleophile hydrazine in ethanol under reflux to afford substituted pyrazoles 4(a–f), 4j, and 4k in good yields. [Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resources: Full experimental and spectral details.]