Driven by the increasing concerns on sustainability, environmental pollution and the advances in processing technology, research on new chemicals is gradually shifting from petroleum feedstock towards viable and renewable alternatives. L-cysteine is naturally abundant and has a great potential of becoming a valuable building block. In this thesis work, we intend to utilize the thiol group of L-cysteine in the thiol-ene click reaction or the reaction with aldehydes for functionalization. In addition, dimerization through the amino-acid group of L-cysteine leads to the formation of diketopiperazines (DKP). The structurally rigid DKPs are a class of naturally occurring cyclic amino acids and are explored as a new cyclic building block for various functional compounds and polymers is this thesis research.
The thesis outlines several synthetic routes to multifunctional compounds and polymers derived from L-cysteine. First, a series of cysteine-based DKP and DKP-containing polymers were synthesized from S-alkylated compounds under mild conditions and in high yields. The chiroptical activity of the obtained diastereomers was detected and present great potential as a high-selective, sensitive sensor for sensing silver ion in aqua system. Next, a series of DKP-containing difunctional monomers were synthesized from 4-thiazolidinecarboxylic acid derivatives. Based on the type of imported functional group, DKP-containing polymers including polyesters and polycarbonates were produced with high molecular weights. Last, linear and star-shaped macromolecules containing L-cysteine at the chain ends were prepared. Their surface tension, pH-sensitivity and self-assembling behaviors were studied. In addition, cyclodextrins and polysaccharides were functionalized with L-cysteine and their potential uses for detection and separation of chiral acids were investigated.