Abstract: | The13C NMR spectra of 22 derivatives of 18 - and 18 -glycyrrhetic acids that have been investigated and an assignment of the signals has been made. It has been shown that a modification of the carboxy group of glycyrrhetic acid leads mainly to a change in the chemical shifts of the -, -, and -carbon atoms of ring E. The assignment of a number of signals has been confirmed by the use of the shift reagent Eu(fod)s. It has been established that the C28 and C16 signals are the most sensitive to a change in the C18 configuration in the spectra of glycyrrhetic acid derivatives.Institute of Chemistry, Bashkir Branch, Academy of Sciences of the USSR, Ufa. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 645–653, September–October, 1985. |