Chiral Polymers from Norbornenes Based on Renewable Chemical Feedstocks.

Optically active polymers are of great interest as materials for dense enantioselective membranes, as well as chiral stationary phases for gas and liquid chromatography. Combining the versatility of norbornene chemistry and the advantages of chiral natural terpenes in one molecule will open up a facile route toward the synthesis of diverse optically active polymers. Herein, we prepared a set of new chiral monomers from cis-5-norbornene-2,3-dicarboxylic anhydride and chiral alcohols of various natures. Alcohols based on cyclic terpenes ((-)-menthol, (-)-borneol and pinanol), as well as commercially available alcohols (S-(-)-2-methylbutanol-1, S-(+)-3-octanol), were used. All the synthesized monomers were successfully involved in ring-opening metathesis polymerization, affording polymers in high yields (up to 96%) and with molecular weights in the range of 1.9 × 105-5.8 × 105 (Mw). The properties of the metathesis polymers obtained were studied by TGA and DSC analysis, WAXD, and circular dichroism spectroscopy. The polymers exhibited high thermal stability and good film-forming properties. Glass transition temperatures for the prepared polymers varied from -30 °C to +139 °C and, therefore, the state of the polymers changed from rubbery to glassy. The prepared polymers represent a new attractive platform of chiral polymeric materials for enantioselective membrane separation and chiral stationary phases for chromatography.

Chiral ß3-isocyanopropionates for multicomponent synthesis of peptides and depsipeptides containing a ß-amino acid fragment.

An efficient three-step synthesis of a novel family of enantiomerically pure isocyanides derived from ß3-isocyanopropionic acids was elaborated. Easily available N-formylated α-amino acids were used as starting materials towards this aim. The 3-step sequence (Arndt-Eistert reaction-Wolff rearrangement-dehydration) resulted in target isonitriles in good yields (up to 97%). As a result a new family of isocyanides bearing a fragment of ß3-amino acids with different functional groups (amides, esters and short peptides) was obtained. It was demonstrated that these new isonitriles can be used in the Ugi and Passerini reactions to prepare short peptides and depsipeptides having a ß-amino acid fragment incorporated.

Diastereoselectivity of Azido-Ugi Reaction with Secondary Amines. Stereoselective Synthesis of Tetrazole Derivatives.

The diastereoselectivity of azido-Ugi reaction with cyclic amines was investigated. It was found that the reaction with α-substituted five- to seven-membered cyclic amines proceeds very efficiently to provide high control of diastereoselectivity (≤100% de) under mild conditions. Target tetrazole-derived products were isolated in excellent yields (≤98%). The reaction has a broad scope in terms of its amine, aldehyde, and isocyanide nature. It was found that the diastereoselectivity of the reaction depends on the ring size of the starting cyclic amines. More rigid piperidines provided the highest selectivity of the reaction. Using benzyl isocyanide, the prepared N-benzyl tetrazoles can be deprotected by hydrogenolysis to form the corresponding NH tetrazoles in high yields.