N-Iodosuccinimide-Promoted [3 + 2] Annulation Reaction of Aryldiazonium Salts with Guanidines To Construct Aminotetrazoles

A N-iodosuccinimide (NIS)-promoted [3 + 2] annulation reaction of aryldiazonium salts with guanidines has been developed for the construction of previously elusive 2-aryl-5-amino-2H-tetrazoles. This transformation takes advantage of readily available starting materials, proceeds under metal-free, mild, and robust conditions, and holds broad functional group compatibility. The utility of this protocol is further manifested via coupling, annulation, deamination, and denitrogenation derivatizations.

Controlling Pd-Catalyzed N-Arylation and Dimroth Rearrangement in the Synthesis of N,1-Diaryl-1H-tetrazol-5-amines

The Pd-catalyzed N-arylation method for the synthesis of eighteen N,1-diaryl-1H-tetrazol-5-amine derivatives is reported. By running the reactions at 35 °C, compounds were isolated as single isomers since the undesired Dimroth rearrangement was completely suppressed. Furthermore, the Dimroth rearrangement of N,1-diaryl-1H-tetrazol-5-amines was rationalized by conducting comprehensive experiments and NMR analysis as well as density functional theory (DFT) calculations of thermodynamic stability of the compounds. It was established that the Dimroth rearrangement is thermodynamically controlled, and the equilibrium of the reaction is determined by the stability of the corresponding isomers. The mechanism was investigated by additional DFT calculations, and the opening of the tetrazole ring was shown to be the rate-determining step. By maneuvering Pd-catalyzed N-arylation and the subsequent Dimroth rearrangement, two more N,1-diaryl-1H-tetrazol-5-amine derivatives were acquired, which otherwise cannot be synthesized by employing the C-N cross-coupling reaction.

Synthesis and in vitro Biological Evaluation of Novel Thymidine Analogs Containing 1H-1,2,3-Triazolyl, 1H-Tetrazolyl, and 2H-Tetrazolyl Fragments

3'-Azidothymidine (AZT) reacts with 1-propargyl-5-R-1H- and 2-propargyl-5-R-2H-tetrazoles (R = H, Me, CH₂COOEt, CH₂CON(CH₃)₂, Ph, 2-CH₃-C₆H₄, or 4-NO₂-C₆H₄) via the Cu(I)-catalyzed asymmetric [3 + 2] cycloaddition to give 3'-modified thymidine analogs incorporating 1H-1,2,3-triazolyl, 1H-, and 2H-tetrazolyl fragments in 41-76% yield. The structures of the obtained compounds have been elucidated by means of HRESI⁺-MS, ¹H and ¹³ C{¹H} NMR, and single crystal X-ray diffraction {for 3'-[4-(1H-5-N,N-dimethylaminocarbonylmethyltetrazol-1-yl)-1H-1,2,3-triazol-1-yl]thymidine 10d}. In vitro biological evaluation of the prepared compounds has been performed; they have exhibited low activity against phenotypic HIV-1_899A. Moderate anti-influenza activity against influenza virus A/Puerto Rico/8/34 (H1N1) strain has been observed in the cases of 3'-(4-(1H-tetrazol-1-ylmethyl)-1H-1,2,3-triazol-1-yl)thymidine 10a (IC₅₀ 39.6 μg/mL), 3'-(4-(2H-5-ethoxycarbonyltetrazol-2-ylmethyl)-1H-1,2,3-triazol-1-yl)thymidine 11c (IC₅₀ 31.6 μg/mL), and 3'-(4-(2H-5-(4-nitrophenyl)-tetrazol-2-ylmethyl)-1H-1,2,3-triazol-1-yl)thymidine 11g (IC₅₀ 46.4 μg/mL). The tested compounds possess very low cytotoxicity towards MDCK and MT4 cells as well as tumor human cervical carcinoma HeLa and promyelocytic leukemia HL-60 cells.

3-(4-Bromo-phen-yl)-1-butyl-5-[1-(2-chloro-6-methyl-phen-yl)-1H-tetra-zol-5-yl]imidazolidine-2,4-dione

In the title mol-ecule, C21H20BrClN6O2, the chloro-substituted benzene ring forms a dihedral angle of 77.84 (7)° with the tetra-zole ring and the bromo-substituted ring forms a dihedral angle of 43.95 (6)° with the imidazole ring. The dihedral angle between the tetra-zole and imidazole rings is 67.42 (8)°. The terminal methyl group of the butyl substituent is disordered over two sets of sites, with refined occupancies 0.67 (3) and 0.33 (3). In the crystal, there is a short Br⋯N contact of 3.183 (2) Å.

Synthesis of peptidomimetics, δ- and ε-lactam tetrazoles

A concise two-step procedure for the synthesis of novel δ-lactam tetrazoles has been established via the Ugi-azide reaction using 5-oxohexanoic acid along with primary amines, isocyanides, and azidotrimethylsilane followed by 1,1'-carbonyldiimidazole-mediated intramolecular amide formation. Expansion to ε-lactam tetrazole scaffolds was accomplished using methyl 6-oxoheptanoate via the same Ugi-azide reaction followed by basic hydrolysis and SOCl(2) activation to enable lactam formation.

Study of [18F]FLT and [123I]IaraU for cellular imaging in HSV1 tk-transfected murine fibrosarcoma cells: evaluation of the tracer uptake using 5-fluoro, 5-iodo and 5-iodovinyl arabinosyl uridines as competitive probes

As one of the most intensively studied probes for imaging of the cellular proliferation, [(18)F]FLT was investigated whether the targeting specificity of thymidine kinase 1 (TK1) dependency could be enhanced through a synergistic effect mediated by herpes simplex type 1 virus (HSV1) tk gene in terms of the TK1 or TK2 expression. 5-[(123)I]Iodo arabinosyl uridine ([(123)I]IaraU) was prepared in a radiochemical yield of 8% and specific activity of 21 GBq/μmol, respectively. Inhibition of the cellular uptake of these two tracers was compared by using the arabinosyl uridine analogs such as 5-iodo, 5-fluoro and 5-(E)-iodovinyl arabinosyl uridine along with 2'-fluoro-5-iodo arabinosyl uridine (FIAU). Due to potential instability of the iodo group, accumulation index of 1.6 for [(123)I]IaraU by HSV1-TK vs. control cells could virtually be achieved at 1.5 h, but dropped to 0.2 compared to 2.0 for [(18)F]FLT at 5 h. The results from competitive inhibition by these nucleosides against the accumulation of [(18)F]FLT implied that FLT exerted a mixed TK1- and TK2-dependent inhibition with HSV1-tk gene transfection because of the shifting of thymidine kinase status. Taken together, the combination of [(18)F]FLT and HSV1-TK provides a synergistic imaging potency.

Synthesis and inhibitory activity of thymidine analogues targeting Mycobacterium tuberculosis thymidine monophosphate kinase

We report on Mycobacterium tuberculosis thymidine monophosphate kinase (TMPKmt) inhibitory activities of a series of new 3'- and 5'-modified thymidine analogues including α- and β-derivatives. In addition, several analogues were synthesized in which the 4-oxygen was replaced by a more lipophilic sulfur atom to probe the influence of this modification on TMPKmt inhibitory activity. Several compounds showed an inhibitory potency in the low micromolar range, with the 5'-arylthiourea 4-thio-α-thymidine analogue being the most active one (K(i)=0.17 μM). This compound was capable of inhibiting mycobacteria growth at a concentration of 25 μg/mL.