(1) Artificial synovial fluid and cartilage. (2) Non-manumitative GD3+ hosts as MRI contrast agents. (3) Five-member heterocycles as switchable ferromagnetic coupling units. (4) Liquid crystal opto-optical switch: Non-destructive information retrieval based on a photochromic fulgide as trigger.

摘要

Chapter I describes the methodology for the construction of hyperbranched carbohydrate polymers. Multilevel selectivity in activation of carbamates to isocyanates with chlorosilanes was achieved by matching chlorosilanes and carbamates under temperature control. t-Butyl carbamate was found to be the most stable while p-nitrophenyl carbamates was the most reactive. Biscarbamates with four pairs of carbamates were synthesized and activated to monoisocyanates. We studied the mechanism of this reaction computationally and found the origin of selectivity in the differences in sigmasigma* interactions. Subsequently, we describe the synthesis of a series of differentially protected chloroacetone synthetic equivalents. The described synthetic methodology allows for access to a variety of chloroacetone equivalents in three high yielding steps. We applied methodology to the synthesis of protected oxonorvaline for solid phase peptide synthesis. The synthesis of oxonorvaline represents a general approach to unnatural aminoacids with acid-sensitive side chains amenable for solid phase peptide synthesis.;Chapter II describes our approach to new MRI contrast agents for improved relaxivity. The synthesis of several pyrrole based building blocks is disclosed.;Chapter III describes a series of 1,3-, 2,5-, and 2,4-dimethylene five-member heterocycles as new ferromagnetic coupling units. Full geometry optimization of structures with heteroatoms ranging from Be to O and from Mg to S at the CASSCF level with energy calculation at the MCQPDT2 level allowed for the discovery of four triplet ground state 2,5-dimethylene heterocycles. The series of 2,4-dimethylene heterocycles yields a family of acid-base driven magnetic switches in which the ground state multiplicity can be changed with protonation, a previously unknown phenomenon. Analysis of the wavefunction revealed that these seemingly disparate groups belong to one superfamily and their properties can be described by a single relationship. The energetic limits of the singlet and triplet preference are found to be -55 kcal/mol and 13 kcal/mol.