ACYLATED C-21 STEROIDAL BISDESMOSIDIC GLYCOSIDES FROM CARALUMA-UMBELLATA

From the whole plant of Caraluma umbellata, three new C-21 steroidal g lycosides, named as carumbellosides III-V, were isolated and their str uctures elucidated by extensive spectroscopic experiments, devoid of a ny derivatisation, as caralumagenin -D-digitalopyranoside-20-O-beta-D- glucopyranoside, caralumagenin ranoside-20-O-(2-O-benzoyl)-beta-D-gluc opyranoside side and caralumagenin anoside-20-O-(2-O-benzoyl)-beta-D-g lucopyranoside. The determination of the absolute configuration of the aglycone as (20R), the conformations of the sugars and the unambiguou s assignments of their NMR spectroscopic signals were achieved by a co mbination of 2D-NMR techniques. The isolates were devoid of significan t cytotoxity in the UIC human cancer cell panel. (C) 1997 Elsevier Sci ence Ltd.