The synthesis of new betulin and ursolic acid derivatives and evaluation of their antiviral activity in vitro is reported. Betulin was modified at positions C-3, C-20 and C-28 to afford the derivatives with nicotinoyl-, methoxycynnamoyl-, alkyne and aminopropoxy-2-cyanoethyl-moieties. The two stage conversion of betulin to the new ursane-type triterpenoid by treatment of allobetulin with Ac(2)O-HClO(4) is suggested. Cyanoethylation of ursonic acid oxime led to cyanoethyloximinoderivative. According to the results of antiviral screening against human papillomavirus type 11 the selectivity index for tested triterpenoids has a range from 10 to 35 with no cellular cytotoxicity, the most remarkable activity was found for 3beta,28-di-O-nicotinoylbetulin. 3Beta,28-dihydroxy-29-norlup-20(30)-yne was also active against HCV replicon (EC(50) 1.32; EC(90) 16.82; IC(50) 12.41; IC(90) >20; SI(50) 9.4; SI(90) >1.19). 28-O-methoxycynnamoylbetulin was active against influenza type A virus (H1N1) (EC(50) 2; IC(50) >200; SI >100).
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