Structural determinations by analytical analysis of 7-phosphanorbornadiene derivatives and amino acid enantiomers

Abstract

The purpose of Chapter 1 is to create a bicyclic, two-coordinate phosphorus derivative in the form of a 2,3-benzo-l,4,5,6-tetraphenyl-7-phosphanorbomadiene anion and measure its experimental 3,P NMR chemical shift. This value is compared to a theoretical NMR shift of 8 +1085 ppm calculated by D.B. Chesnut at Duke University using ab initio quantum mechanics. This is the largest downfield chemical shift ever predicted for an organophosphorus compound. Diphenylacetylene was reacted with solid Li to produce l,4-dilithio-l,2,3,4-tetraphenylbutadiene (LTPB). Then, LTPB was reacted with dichlorophenylphosphine to produce pentaphenylphosphole, which was oxidized with 30% hydrogen peroxide to pentaphenylphosphole oxide. Next, this oxide was reacted with benzyne to synthesize 2,3-benzo-l,4,5,6,7- pentaphenyl-7- phosphabicyclo[2.2. l]hept-5-ene oxide which has a 31P NMR chemical shift of 8 + 96 ppm. Reduction of this product using trichlorosilane afforded products with 31P NMR chemical shifts o f 8 +57 and +58 ppm which could possibly be the two isomers of 2,3-benzo-l,4,5,6,7- pentaphenyl-7- phosphabicyclo[2.2. l]hept-5-ene. Further reduction of these crude products was attempted using elemental sodium but with no success. Because of a time restraint and the difficulty in obtaining a stable 7-phosphanorbomadiene, the bicyclic, two- coordinate anionic phosphorus derivative could not be synthesized and proven to have a 31P NMR chemical shift of 8+1085 ppm. Amino acid racemization occurs according to the environment to which the amino acids are exposed. Racemization occurs when laevorotary-forms of amino acids are converted to dextrorotary-forms of amino acids by exposure to weak acids or bases, over time. This conversion in ancient samples was found to take place at the same rate as degradation of DNA. It was found [1] that if the D/L ratio of aspartic acid was lower than 0.08 in a bone or tissue sample, viable DNA could be extracted from it In Chapter 2 this research attempted to derivatize enantiomeric amino acids with L-Marfey’s Reagent to produce diastereomers that could be separated using capillary electrophoresis, gas chromatography, and high pressure liquid chromatography. Problems with the equipment, contamination, unrepeatable results and a variety of unknown factors plagued this portion of the research. This mode of testing for the presence of viable DNA was deemed a non-viable process.