Numerous medicinally important compounds are chiral. Compounds which are chiral by virtue of hydrogen-deuterium substitution, or hydrogen-deuterium-tritium substitution, (chiral methyl group) have played important roles in the elucidation of biochemical mechanisms. However, there is a distinct need for better general methods for the asymmetric synthesis of compounds in these categories. We propose to investigate the utility of a new class of chiral pseudotetrahedral organorhenium compounds, (Eta-C5H5)Re(NO)(PPh3)(X), as chiral auxiliaries in asymmetric organic synthesis. These complexes are easy to synthesize and obtain optically pure. Several reactions have been discovered where the rhenium-centered chirality is stereospecifically transferred to a new ligand-based chiral center. Through labeling experiments, X-ray, crystallography, and MO calculations, we seek to define the mechanistic basis for this asymmetric induction. Among many synthetic objectives, we intend to (a) prepare chiral rhenium alkyls-CHRR' and stereospecifically cleave the Re-C bond to chiral organic molecules XCHRR'; (b) utilize similar methods for the synthesis of organic compounds with hydrogen-deuterium and hydrogen-deuterium-tritium chirality (XCHDR, XCHDT); (c) utilize nucleophilic rhenium vinyl, acetylide, and phenyl complexes for the stereoselective or stereospecific construction of chiral centers Beta (or Delta) to the metal; (d) investigate the ability of rhenium-substituted dienes to participate in asymmetric Diels-Alder reactions; (e) attempt the generation of carbanions Alpha and Beta to the rhenium and investigate their utility for asymmetric alkylations; (f) investigate the stereoselectivity of nucleophilic attack upon rhenium-coordinated aldehydes; (g) investigate the utility of rhenium alkylidenes for asymmetric olefin cyclopropanation, and rhenium peracids for asymmetric epoxidation. From this program of fundamental research, we expect that improved syntheses of several types of medicinally important compounds will ultimately be realized.
