PREGNANE GLYCOSIDES FROM STAPELIA-VARIEGATA

Eleven new pregnane ester glycosides have been isolated from the aeria l parts of Stapelia variegata. Eight of the recognized compounds were established to possess the same trioside moiety, viz. -D-cymaropyranos yl-(1-4)-beta-D-cymaropyranoside]. These compounds were identified as: stavaroside A: 12-O-beta-angeloyl-20-O-benzoyl sarcostin; stavaroside B: 12-O-beta-angeloyl-20-O-tigloyl sarcostin; stavaroside C: 11 alpha -acetoxy 2 beta-benzoxy-3 beta,8 beta,14 beta-trihydroxy-pregn-5-ene-2 0-one; stavaroside D: 11 alpha-acetoxy-12 beta-tigloxy-3 beta,8 beta,1 4 beta-trihydroxy-pregn-5-ene-20-one; stavaroside E: 12-O-beta-benzoyl sarcostin; stavaroside F:11 alpha-acetoxy- 12 beta-acetoxy-3 beta, 8 beta, 11 beta, 12 beta, 14 beta-trihydroxy-pregn-5-ene-20-one; stavaro side G: 12-O-beta,20-O-diacetyl sarcostin and stavaroside H: 3 beta, 8 beta, 11 alpha, 12 beta, 14 beta-pentahydroxy-pregn-5-ene-20-one. The other three compounds were shown to possess the same tetraside sugar moiety, Viz. 3-0- [beta-D-glucopyranosyl-(1-4)-3-O-methyl- eta-D-allop yranosyl-(1-4)-beta-D-cymaropyranosyl-( 1-4)-beta-D-cymaropyranoside]. These compounds were identified as: stavaroside I: 1 alpha, 12 beta-a ngeloxy and benzoxy-3 beta, 8 beta, 14 beta-trihydroxy-pregn-5-ene-20- one; stavaroside J: 11 alpha-acetoxy-12 beta-benzoxy-3 beta,8 beta, 14 beta-trihydroxy-pregn-5-ene-20-one and stavaroside K: 11 alpha-acetox y-12 beta-tigloxy-3 beta,8 beta,14 beta-trihydroxypregn-5-ene-20-one. The structural elucidation of the isolated compounds was aided signifi cantly on the basis of the chemical and spectral evidence. The decisiv e assignments of the ester positions were based on the Inverse Detecte d-Heteronuclear Multiple Bond Connectivity (HMBC) experiments.