(3S)-Tosyl-24-methyl-elemo-lanosta-8,24(31)-diene-7,11-dione

To a solution of 1¹ (1g, 1.68mmol) in 20ml of acetone, was added (0.50g, 0.85mmol) of chromic anhydride². The mixture was maintained at 0°C during 24h, and washed with 20ml of cold water. Extracted with ethyl acetate, the organic layer was dried over Na₂SO₄ , and evaporated under reduced pressure. The residue was purified on a silica gel column using hexane/EtOAc (98/2) as eluant to give 2 (0.63g, 60%).

Mp: 160-161 °C (Hexane).

MS (EI, 70eV) : 622 (M^+.).

¹H NMR (300 MHz, CDCl₃) d(ppm): 4.15 (dd,J₁=12, J₂= 4Hz , H-3); 2.43 (s, 3H of tosyle group); 1.22 and 1.25 (2s, 3H-26 , 3H-27); 4.63 and 4.69 (2S, 2H-31).

¹³C NMR (75 MHz, CDCl₃) d(ppm): 89.10 C-3 ; 150.00; 155.00 C8 and C9 ; 199.50; 201.50 C7 and C11; 155.50 C-24 ; 106.50 C-31 ; 121.31 ; 124.36 ; 124.43 ; 126.55, 131.45 and 141.34 (aromatic carbons) IR n(cm^-1): 1700 cm^-1.