1,5-disubstituted 1,2,3-triazolylated carbohydrates and nucleosides

In general, 1,5-disubstituted 1,2,3-triazolyl moiety is much less common in the synthesis and applications in comparison to its regioisomeric counterpart. Moreover, the synthesis of 1,5-disubstituted 1,2,3-triazoles are not so straightforward as is the case for copper catalyzed strategy of 1,4-disubstituted 1,2,3-triazoles. The preparation of 1,5-triazolylated carbohydrates and nucleosides are even more complex because of the difficulties in accessing the appropriate starting materials as well as the compatibility of reaction conditions with the various protecting groups. 1,5-Disubstitution regioisomeric triazoles of carbohydrates and nucleosides were traditionally obtained as minor products through straightforward heating of the mixture of azides and terminal alkynes. However, the separation of isomers was tedious or in some cases futile. On the other hand, regioselective synthesis using ruthenium catalysis triggered serious concern of residual metal content in therapeutically important ingredients. Therefore, serious efforts are being made by several groups to develop non-toxic metal based or completely metal-free synthesis of 1,5-disubstituted 1,2,3-triazoles. This article strives to summarize the pre-Click era as well as the post-2001 reports on the synthesis and potential applications of 1,5-disubstituted 1,2,3-triazoles in biological systems.

Readily accessible azido-alkyne-functionalized monomers for the synthesis of cyclodextrin analogues using click chemistry

A set of linear and cyclic oligomers were synthesized starting from a suitable azido-alkyne monomer through click oligomerization. The synthesis of these monomers starting from bromobenzene features an enzymatic dihydroxylation...

Radiolabeled Angiogenesis-Targeting Croconaine Nanoparticles for Trimodality Imaging Guided Photothermal Therapy of Glioma

To meet the criteria of effective theranostics, biocompatible nanomedicine endowing intrinsic therapeutic and imaging properties have gained extraordinary momentum. In this study, an ultra-stable near-infrared (NIR) dye croconaine (CR780) was engineered with arginine-glycine-aspartic acid (RGD) peptide and polyethylene glycol (PEG), which was then self-assembled into uniform nanoparticles (NPs). These RGD-CR780-PEG5K assemblies were radiolabeled with ¹²⁵I through a facile standard Iodo-Gen method. The resulting [¹²⁵I]RGD-CR780-PEG5K NPs showed effective accumulation in α_vβ₃ integrin expressing glioblastoma, as evidenced by single photon emission computed tomography (SPECT)/CT and NIR fluorescence imaging. More importantly, high-resolution photoacoustic imaging revealed that these NPs selectively targeted to angiogenic tumor vessels. With the favorable tumor selective accumulation and high photothermal conversion efficiency, the [¹²⁵I]RGD-CR780-PEG5K NPs allowed thorough tumor ablation and inhibition of tumor relapse at a relatively low laser energy (0.5 W/cm²). Overall, this work offers a proper methodology to fabricate tumor-targeted multi-modal nanotheranostic agents, providing great opportunity for precision imaging and cancer therapy.

A Review on Recent Syntheses of Amaryllidaceae Alkaloids and Isocarbostyrils (Time period mid-2016 to 2017)

Alkaloids from the Amaryllidaceae have become valuable targets for synthetic organic chemists, mainly due to their wide variety of bioactivities and potential for utilization in medicinal chemistry ventures. In addition, the structural complexity of a number of these alkaloids has also been a reason for the interest in these compounds. In this review, the last 18 months of literature was perused and synthetic highlights have been presented here, with the hope to further focus attention on this interesting class of compounds and to encourage others to synthesize these compounds and their derivatives and/or analogues. The review contains examples of syntheses from most of the important alkaloid scaffold classes previously isolated from the Amaryllidaceae, namely: lycorine, crinine, galanthamine, tazettine, montanine, phenanthridone, phenanthridine, plicamine, mesembrine and some minor scaffolds (like gracilamine).