|Title of Thesis or Name of the Project:
I. Stereochemistry of Flavans II. Synthesis in the Penicillin Series
A rigorous assignment of NMR signals of flavan-3,4-diol esters was made for the first time by examining NMR spectra of 4-deuterioflavan-3,4-diol esters. Relative stereochemistry of several flavan-3,4-diols was deduced from coupling constant values, and this method was extended to flavan-3,4-dibromides and several compounds derived from them. The NMR spectra of flavan-4α and 4β-ol benzoates were analyzed making possible the first unequivocal assignment of the stereochemistry of flavan-4-ols.
Construction of the seven-membered ring periphery and subsequent transannular reactions to form fused thiazolidine β-lactams was investigated as a route to penicillins. Efficient syntheses were developed for the desired monocyclic intermediates (such as 1).
Subsequent attempts to form the [3.2.0] bicyclic system of penicillins by nucleophilic displacement at C7 by N4 or at N4 by C7 were unsuccessful. UV irradiation of 2 and several similar compounds gave inseparable mistures which gave no penicillin derivatives on hydrolysis.