Oxidation of thiazolo[3,2-a]pyrimidin-3(2H)-ones with DMSO and Lawesson’s reagent

Diarylation of thiazolopyrimidines by laccase and their in vitro evaluation as antitumor agents

A mild and efficient method was developed for the synthesis of new derivatives of thiazolo[3,2-a] pyrimidin-3(2H)-ones from available starting materials based on the oxidation of catechols to ortho-quinone by Myceliophthora thermophila laccase (Novozym 51,003) and 1,4-addition of active methylene carbon to these in situ generated intermediates in moderate to good yields (35-93%). The structure of the products was confirmed through ¹H NMR, ¹³C NMR, HMBC, HSQC, DEPT-135, and mass spectroscopy techniques. These novel compounds were evaluated as active antitumor agents against human colorectal adenocarcinoma and liver adenocarcinoma cell lines. All compounds displayed potent inhibition activities against the HT-29 cell line with IC₅₀ values of 9.8-35.9 µM, superior to the positive control doxorubicin, and most showed potent anticancer activities against the HepG2 cell line.

Synthesis, Self-Assembly in Crystalline Phase and Anti-Tumor Activity of 2-(2-/4-Hydroxybenzylidene)thiazolo[3,2-a]pyrimidines

A series of new thiazolo[3,2-a]pyrimidines different by aryl substituents in 2 and 5 positions are synthesized and characterized in solution as well as in the crystalline phase using ¹H and ¹³C NMR-, IR-spectroscopies, mass-spectrometry methods, and single crystal X-ray diffraction (SCXRD). The SCXRD study revealed the role of intermolecular H-bonding in the formation of supramolecular architectures (racemic monomers, centrosymmetric racematic dimers, or homochiral 1D chains) of obtained thiazolo[3,2-a]pyrimidines derivatives depending on solvents (aprotic DMSO or protic EtOH) used upon the crystallization process. Moreover, the in vitro study of cytotoxicity toward different tumor cells showed their high or moderate efficiency with moderate cytotoxicity against normal liver cells which allows to consider the obtained thiazolo[3,2-a]pyrimidine derivatives as promising candidates for application as antitumor agents.

Crystalline State Hydrogen Bonding of 2-(2-Hydroxybenzylidene)Thiazolo[3,2-a]Pyrimidines: A Way to Non-Centrosymmetric Crystals

Thiazolopyrimidines are attractive to medical chemists as new antitumor agents due to their high inhibiting activity towards the tumor cells replication process and easy modification of their structure by varying of the number and nature of substituents. The presence of asymmetric C5 carbon atoms requires the development of racemic mixture separation procedures for these heterocycles. One of the more effective ways is the crystallization of a racemic compound as a conglomerate. A prerequisite for such separation is the formation of non-centrosymmetric crystals presenting Sohncke space groups. For the construction of chiral supramolecular ensembles in a crystalline state, hydrogen bonds were chosen as supramolecular synthons. In this context, salicylic derivatives at the C2 atom of thiazolopyrimidines were synthesized. The crystal structures of the obtained compounds were established by SCXRD. The regularities of the solvent’s influence on the crystal packaging were revealed. The conditions for the preparation of crystals with the chiral space group due to intermolecular hydrogen bonds were discovered.

Synthesis, Crystal Structure, and Biological Evaluation of Fused Thiazolo[3,2-a]Pyrimidines as New Acetylcholinesterase Inhibitors

A new series of thiazolo[3,2-a]pyrimidine bromide salt derivatives 7a–d were synthesized from 3,4-dihydropyrimidinethione precursors. The target compounds were fully characterized by 1D- and 2D-NMR, high resolution ESI-MS/MS and single crystal X-ray diffraction analysis, which confirmed a regioselective 5H cyclization of the dihydropyrimidinethiones. All target compounds were evaluated in vitro as human acetylcholinesterase (hAChE) inhibitors via an Ellman-based colorimetric assay and showed good inhibition activities (better than 70% at 10 µM and IC₅₀ values in the 1 µM range). Molecular docking simulations for all target products into hAChE were performed and confirmed strong binding to the enzyme. These results provide a promising and new starting point to improve acetylcholinesterase inhibitors and explore novel treatment options against Alzheimer’s disease.

Syntheses and bioactivities of songorine derivatives as novel G protein-coupled receptor antagonists

Songorine isolated from Aconitum brachypodum Diels possesses prominent activity of inhibiting G protein-coupled receptors (GPCRs) in the early screening process. In this paper, a series of Songorine derivatives were synthesized and their inhibitory activities on GPCRs were also evaluated by using the Double Antibody Sandwich ELISA (DAS-ELISA) in vitro. Among them, three derivatives (3a, 4, 7) exhibited significant inhibitory activity against GPCRs with IC₅₀ values of 0.08-0.29 nM. Moreover, the structure-activity relationships (SARs) of songorine derivatives were discussed in detail. They have great potentials as novel GPCRs antagonists in the future.