| abstract |
The invention relates to novel betulinic acid derivatives of formula (I), wherein R is C(═CH 2 )CH 3 or CH(CH 3 ) 2 ; R 2 together with the adjacent carbonyl group forms a carboxylic acid, carboxylic acid ester or amide or substituted amide; R 3 or R 4 are hydrogen or aryl with the proviso that both are not independently hydrogen or alkyl or R 3 and R 4 are combined together to form an aryl ring optionally substituted with a group X, wherein X is selected from halogen, alkyl, cyano, nitro, alkoxy, amino or substituted amine; Y is N or O; and R 1 is zero when Y is O, and R 1 is hydrogen, alkyl or aryl alkyl when Y is N, useful for inhibition of tumor cancer cells. |