Parallel modification of tropane alkaloids

Various tropane alkaloids have been prepared by structural modification of the readily available natural product, scopolamine 1. Reaction of isocyanates with 6,7-dehydrotropine 5 provided a number of urethanes 6a-e. Reductive amination of tropinone 7 and subsequent reaction with isocyanates provided ureas 9a-f. Mitsunobu inversion of the C-3 alcohol of tropine 10 afforded the epimeric ester 11

Clean and efficient synthesis of O-silylcarbamates and ureas in supercritical carbon dioxide

The synthesis of a family of O-silylcarbamates from the corresponding silylamines has been achieved simply by heating the silylamine in supercritical carbon dioxide (scCO<sub>2</sub>), and these O-silylcarbamates have been shown to be effective precursors for the synthesis of a range of symmetrical and unsymmetrical ureas

Thermo-Induced Self-Assembly of Responsive Poly(DMAEMA‑<i>b</i>‑DEGMA) Block Copolymers into Multi- and Unilamellar Vesicles

A series of thermoresponsive diblock copolymers of poly­[2-(dimethylamino)­ethyl methacrylate-<i>block</i>-di­(ethyleneglycol) methyl ether methacrylate], poly­(DMAEMA-<i>b</i>-DEGMA), were synthesized by reversible addition–fragmentation chain transfer (RAFT) polymerizations. The series consist of diblock and quasi diblock copolymers. Sequential monomer addition was used for the quasi diblock copolymer synthesis and the macro-chain transfer approach was utilized for the block copolymer synthesis. The focus of this contribution is the controlled variation of the ratios of DMAEMA to DEGMA in the copolymer composition, resulting in a systematic polymer library. One of the investigated block copolymer systems showed double lower critical solution temperature (LCST) behavior in water and was further investigated. The phase transitions of this block copolymer were studied in aqueous solutions by turbidimetry, dynamic light scattering (DLS), variable temperature proton nuclear magnetic resonance (¹H NMR) spectroscopy, zeta potential, and cryo transmission electron microscopy (cryo-TEM). The block copolymer undergoes a two-step thermo-induced self-assembly, which results in the formation of multilamellar vesicles after the first LCST temperature and to unilamellar vesicles above the second LCST transition. An interplay of ionic interactions as well as the change of the corresponding volume fraction during the LCST transitions were identified as the driving force for the double responsive behavior