STRUCTURAL STUDIES ON PENICILLIN DERIVATIVES .I. CONFIGURATION OF PHENOXYMETHYL PENICILLIN SULFOXIDE

From a study of nuclear Overhauser effects (NOE) in phenoxymethyl penicillin (III), phenoxymethyl penicillin sulfoxide (IV), and phenoxymethyl penicillin sulfone (V), it has been possible to assign the methyl signals in the nmr spectra of these compounds and to derive information regarding thiazolidine ring conformation in solution. Using the McConnell approach to chemical-shift calculations, aromatic solvent-induced shifts (ASIS), and hydrogen-bonding studies, the sulfoxide configuration of IV is indicated to be (S). The configuration of the sulfoxide IV is verified by an X-ray crystallographic investigation which also shows that basic conformational differences exist between III and IV. The molecular anisotropy of the sulfoxide bond is discussed in both qualitative and quantitative terms. A mechanistic rationale for the formation and existence of one isomer of IV is presented. © 1969, American Chemical Society. All rights reserved.