Dendritic architectures by orthogonal thiol-maleimide "click" and furan-maleimide dynamic covalent chemistries.

A set of dendrons and dendrimers is synthesized divergently using an orthogonal combination of kinetically-driven thiol-maleimide "click" chemistry and thermodynamically reversible furan-maleimide cycloaddition/retrocycloaddition reactions. Growth is controlled by taking advantage of the selective thiol-ene addition of thiols to the electron withdrawn alkene of maleimide in the presence of electron rich alkene of oxanorbornene. Subsequent activation of growing dendrons/dendrimers requires only heat to induce the dynamic covalent liberation of peripheral furan protecting groups.

Development of self-assembled phytosterol based nanoassemblies as vehicles for enhanced uptake of doxorubicin to HeLa cells.

Nanoscale supramolecular systems have been increasingly gaining importance as drug release vehicles due to their ability to target tumor cells. In this work, we have developed a new class of nanoassemblies derived from the phytosterol 24-EpiBrassinolide (EpiB) for the development of nanocarriers for the anticancer drug Doxorubicin (DOX). EpiB is a biocompatible cholesterol mimic, and has inherent apoptotic properties toward cancer cells.

Evaluating Nucleophile Byproduct Formation during Phosphine- and Amine-Promoted Thiol-Methyl Acrylate Reactions.

The commonly accepted mechanism of nucleophile-initiated thiol-acrylate reactions requires the formation of undesired nucleophile byproducts. A systematic evaluation of the formation of such nucleophile byproducts has been carried out to understand the relationships between byproduct formation and nucleophile structure, stoichiometry, solvent, and reaction type. Three common nucleophiles for thiol-Michael reactions were investigated: dimethylphenylphosphine (DMPP), diethylamine (DEA), and hexylamine (HA).

Investigation and Demonstration of Catalyst/Initiator-Driven Selectivity in Thiol-Michael Reactions.

Thiol-Michael "click" reactions are essential synthetic tools in the preparation of various materials including polymers, dendrimers, and other macromolecules. Despite increasing efforts to apply thiol-Michael chemistry in a controlled fashion, the selectivity of base- or nucleophile-promoted thiol-Michael reactions in complex mixtures of multiple thiols and/or acceptors remains largely unknown. Herein, we report a thorough fundamental study of the selectivity of thiol-Michael reactions through a series of 270 ternary reactions using H NMR spectroscopy to quantify product selectivity.