Selective Protection of 2‘,2‘-Difluorodeoxycytidine (Gemcitabine)

Abstract

Gemcitabine (1) is a promising new anticancer agent used in pancreatic cancer. Improvement in the selective targeting of compound 1 and other cytotoxic agents to solid tumors may be enhanced by conjugation to ligands that target peripheral benzodiazepine receptors (PBRs) located on mitochondria and known to be overexpressed in human brain tumors. Development of such chemical conjugates requires selective protection on 4-NH(2), 3'-OH, and 5'-OH of compound 1. All three monoprotected and three diprotected gemcitabine derivatives (2 to 7) were synthesized in good yield by employing a single commonly used protecting reagent, di-tert-butyl dicarbonate, under different conditions. Consequently, the three mono-ligand-gemcitabine conjugates coupled at 4-NH(2), 3'-OH, and 5'-OH respectively (14 to 16) were synthesized in high yield using the PBR ligand PK11195. This selective protection/deprotection strategy offers a relatively straightforward means to modify other nucleosides.

Synthesis of a covalent gemcitabine-(carbamate)-[anti-HER2/neu] immunochemotherapeutic and its cytotoxic anti-neoplastic activity against chemotherapeutic-resistant SKBr-3 mammary carcinoma

“…Phase-II: synthesis of gemcitabine-(carbamate)-PMPI sulfhydryl-reactive intermediate Gemcitabine (10 mg/ml stock in DMSO) was combined with N-[p-maleimidophenyl]-isocyanate (PMPI) 65-67 at a 5:1 molar ratio in combination with constant gentle stirring at 25°C for 3.5 h so that the isocyanate moiety of PMPI which exclusively reacts with hydroxyl (R-OH) groups preferentially created a carbamate covalent bond at the terminal C 5 -methylhydroxy group of gemcitabine. 61,[68][69][70][71][72][73] The highly selective reaction is reportedly complete within 2 h under the applied conditions. Gemcitabine was formulated at a large molar excess to deplete un-reacted PMPI and maximize synthesis of the sulfhydryl-reactive maleimide intermediate as validated by high-performance thin-layer chromatography analysis (HP-TLC).…”

“…One methodology involves creation of a covalent bond at the cytosine amine group of gemcitabine either as a direct link to a 'targeting' ligand or for the purpose of creating a gemcitabine reactive intermediate. 30,71,73,92,93 Similar molecular strategies have been employed to synthesize covalent anthracycline immunochemotherapeutics through the formation of a covalent bond with the a-monoamine (C 3 -amine) group on the carbohydrate moiety of doxorubicin, daunorubicin, or epirubicin. 10,15,17,[20][21][22][23][24][25]27,28,32,19 Generation of a covalent bond at the C 5 -methylhydroxy group of gemcitabine represents a second alternative molecular strategy for synthesizing covalent gemcitabineligand conjugates.…”

“…10,15,17,[20][21][22][23][24][25]27,28,32,19 Generation of a covalent bond at the C 5 -methylhydroxy group of gemcitabine represents a second alternative molecular strategy for synthesizing covalent gemcitabineligand conjugates. 61,[68][69][70][71][72][73] Gemcitabine has been covalently bound to a number of biologically relevant ligands. Most prominent in this regard have been poly-L-glutamic acid (polypeptide configuration), 70 Few if any reports have described the molecular design and efficacy evaluation of a covalent immunochemotherapeutic synthesized through the generation of a covalent bond structure at either the cytosine amine or C 5 -methylhydroxy groups of gemcitabine.…”

Synthesis of Gemcitabine-(C<sub>4</sub>-<i>amide</i>)-[anti-HER2/<i>neu</i>] Utilizing a UV-Photoactivated Gemcitabine Intermediate: Cytotoxic Anti-Neoplastic Activity against Chemotherapeutic-Resistant Mammary Adenocarcinoma SKBr-3

“…Under these conditions the PMPI isocyanate moiety exclusively reacts with hydroxyl (R-OH) groups and preferentially creates a carbamate covalent bond at the terminal C 5 -methylhydroxy group of gemcitabine [36,40,56-61]. The highly selective reaction is reportedly complete within 2 hours under the conditions applied as described.…”

Tumor-targeted polymeric nanostructured lipid carriers with precise ratiometric control over dual-drug loading for combination therapy in non-small-cell lung cancer

“…33 The multiple peaks at 2.55-2.7 ppm might have been the protons of -CO-CH 2 -CH 2 -CO-( Figure S1). This further confirmed that succinyl-GEM conjugation occurred via ester formation.…”