Abstract: Two samples(1^#,2^#)of 3-formhydrazone-rifamycin SV produced by fermentation and chemieal modification have different physical and chemical properties.In this paper,their structures were determined by various kinds of NMR spcctra, such as ¹H,¹³C,DEPT,¹H-¹H COSY,¹H-¹³C COSY and LR ¹H-13 C COSY in inverse mode, and by the absorption spectra of IR and UV-Vis.It was found that the two samples were the main product of amide mode (1^#) and the isomer of iminol mode (2^#). Based on the results of experiments,the isomerization of sample 1^# was discussed.

Key words: 3-formhydrazone-rifamycin SV, Isomerization, 2D NMR, IR, UV-Vis