Chiroptical properties, structure, and absolute configuration of heterosubstituted 2(5H)-furanones

Abstract

Chiroptical properties of a series of 3 and/or 4-heterosubstituted 2(5H)-furanones were investigated with respect to correlation with absolute configuration. The n − π* and π − π* Cotton effects have been assigned on the basis of comparison with the UV spectra in solvents of varying polarity. It is demonstrated that the n − π* transition in 4-amino substituted 2(5H)-furanones appears at shorter wavelength with respect to the π − π* transition. With the exception of 4-pyrrolidino and 4-benzylamino substituted 2(5H)-furanones, other heterosubstituted 2(5H)-furanones follow the butenolide configurational rule (Gawronski et al. J. Org. Chem. 61:1513–1515, 1996). Absolute configuration of 2(5H)-furanone derivatives can also be assigned according to the sign of the Cotton effect (of unknown origin) at 200–230 nm. The structure of four representative sulfur and nitrogen substituted 2(5H)-furanones has been analyzed by X-ray diffraction. The results indicate planarity of the furanone ring and extended conjugation in 4-amino substituted 2(5H)-furanones. Chirality 9:537–544, 1997. © 1997 Wiley-Liss, Inc.