Room-Temperature Accessible Stereospecific Synthesis of Methyl-(Z)-2-(7-methyl-3-oxo-5H-thiazolo[3,2-a]pyrimidin-2(3H)-ylidene)acetates:Cd2+ Fluorescence Probe and DU145 Cell Study

Abstract

Stereospecific synthesis of Methyl-(Z)-2-(7-methyl-3-oxo-5H-thiazolo[3,2-a]pyrimidin-2(3H)-ylidene)acetates 3(a–t) is designed and explored their application as fluorescent probes for Cd²⁺ ions for the first time. These analogs are synthesized via one-pot reaction of (R/S)-2-thioxo-3,4-dihydropyrimidine-5-carboxanilides (TDHPM-5-carboxanilides) with dimethyl acetylenedicarboxylate in MeOH (methanol) as a reusable green solvent at room temperature (RT). Two new C(sp²)N, C(sp²)S sigma bonds, and one new C-N π-bond are formed during this transformation, achieving yields of up to 99%. This protocol demonstrates a low environmental factor (E-factor) (0.09 to 0.35), high atom economy (94.83%), and carbon efficiency (142.68%), reflecting a significant advancement in green chemistry. Compound 3a is synthesized in 99% yield on a gram scale. Compound 3p proves to be an excellent fluorescent probe for Cd²⁺ ions, showing a ninefold increase in fluorescence intensity. The limit of detection and limit of quantification for 3p with Cd²⁺ ions are 7.5 and 25 μM, respectively, with an R² value of 0.9903. Density functional theory calculations revealed that Cd²⁺ ions bind effectively in the cavity of 3p through a ligand-to-metal charge transfer mechanism. Cell viability assays and docking studies show that compounds 3g, 3h, 3p, and 3t exhibited potent activity against the DU145 prostate cancer cell line, with binding affinities of −7.7, −6.8, −8.1, and −7.5 kcal mol⁻¹.