2-Dimethylaminopyridine → (1R,3aS,5aR,5bR,7aR,9S,11aR,11bR,13aR,13bR)-9-(4-hydroxy-2,2-dimethyl-4-oxo-butanoyl)oxy-1-isopropenyl-5a,5b,8,8,11a-pentamethyl-1,2,3,4,5,6,7,7a,9,10,11,11b,12,13,13a,13b-hexadecahydrocyclopenta[a]chrysene-3a-carboxylic acid

Participants

Reaction Steps

3-O-(2',2'-dimethylsuccinyl)betulinic acid (2) was prepared as above using a solution of betulinic acid, dimethylaminopyridine, and dimethylsuccinic anhydride in anhydrous pyridine. The yield was 3.1%. Crystallization form methanol gave colorless needles, melting point 279°-280° C.; [α]D19 +36.2° [c=0.35, CHCl3-MeOH (1:1)]; positive FABMS m/z 585 (M+H)+ ; Negative FABMS m/z 583 (M-H)- ; HR-FABMS calculated for C36H57O6 585.4155, found m/z 585.4156; 1H NMR (pyridine-d5): 0.75, 0.93, 1.03 (×2), 1.06 (each 3H, s; 4-(CH3)2, 8-CH3, 10-CH3, 14-CH3), 1.49 (6H, 2, 2'-CH3 ×2), 1.80 (3H, s, 20-CH3), 2.94 (2H, s, H2-3'), 3.55 (1H, m, H-19), 4.77 (1H, dd, J=5, 11.5 Hz, H-3), 4.79, 4.95 (each 1H, br s, H-30).

Provenance & Evidence