Reaction Steps
To a stirred solution of 20β-t-butyldimethylsilyloxy-3β, 14-dihydroxy-5β,14β-pregnane (see FIG. 6) (420 mg) in dichloromethane (60 ml) was added Fetizons reagent (10 g) and, over 10 minutes, a solution of triacetoxybromorhamnose (2.55 g) in dichloromethane (30 ml). After 3 hours the reaction mixture was washed thoroughly with sodium hydrogen carbonate, water, dried over sodium sulfate and evaporated to give a residue which was dissolved in tetrahydrofuran (50 ml) and treated with tetra-n-butlyammonium fluoride (352 mg) for 16 hours, water was added and the mixture extracted with ether to give a product which was dissolved in methanol (20 ml), triethylamine (20 ml) and water (2 ml) and allowed to stand at room temperature for 72 hours under argon. The reaction mixture was evaporated to dryness and the residue dissolved in methanol and placed on silica gel (20 g) and the solvent allowed to evaporate. The silica gel was washed with petroleum ether (30/60) and dichloromethane. Elution with 8- 10% methanoldichloromethane gave fractions of the α-L-rhamnoside (FIG. 6) (170 mg) recrystallized from methanol-water to give (81 mg) mp 243°-246° C. 1H nmr (CDCl3 :CD3OD, 1:1) δ:0.95,(19CH3), 0.97, S(18CH3), 1.27, DD, J=6.2Hz(6'CH3), 2.27,S(21CH3), 2.96,dd, J=4.1,9.3Hz(17αH), 3.40,t, J=9.5Hz(4'H), 3.64-3.76, m(3'H and 5'H), 3.82,dd,j=1.7, 3.3 Hz (2'H), 3.95, s, w1/2 7 Hz (3H), 4.30, s(ROH), 4.80, d, J=1.5 Hz (1'H)ppm; 13C nmr (CDCl3 :CD3OD,1:1) δ:31.0a (1), 27.0b (2), 72.6c (3), 30.3a (4), 37.5(5), 27.2b (6), 22.1d (7), 40.6(8), 35.7(9), 35.8 (10), 21.3d (11), 39.7(12), --(13), 86.2(14) 34.3(15), 25.4(16), 63.0(17), 15.5(18), 24.1(19), 219.4(20), 33.1(21), 98.8(1'), 72.0c (2'), 72.0c (3'), 73.4c (4'), 69.0(5'), 17.7(6') ppm. Anal. C 65.87; H, 9.63 C27H46O7.1/2H2O requires C, 65.96; H, 9.64.
