摘要
28-Carboxymethoxy lupane tritepenoids 3 and 4 were synthesized by alkylation of betulin with the THP protected 2- hydroxyethyl iodide followed by oxidation and reduction. Direct reaction of betulin （5） or betulone （10） with ethyl bromoacetate led to 28-O-acylation, instead of 28-O-alkylation. The targeted compounds 3 and 4 were not cytotoxic at the highest concentration tested （75 μmol/L）, suggesting that elongation of the chain length at the 28-position in both betulinic acid （1） and betulonic acid （2） was detrimental to the cytotoxicity. The acylation products 28-O-bromoacetates （Sa, 8b and 11） and 28-O-methoxyacetate 13 exhibited cytotoxicity against several cancer cell lines tested.
28-Carboxymethoxy lupane tritepenoids 3 and 4 were synthesized by alkylation of betulin with the THP protected 2- hydroxyethyl iodide followed by oxidation and reduction. Direct reaction of betulin （5） or betulone （10） with ethyl bromoacetate led to 28-O-acylation, instead of 28-O-alkylation. The targeted compounds 3 and 4 were not cytotoxic at the highest concentration tested （75 μmol/L）, suggesting that elongation of the chain length at the 28-position in both betulinic acid （1） and betulonic acid （2） was detrimental to the cytotoxicity. The acylation products 28-O-bromoacetates （Sa, 8b and 11） and 28-O-methoxyacetate 13 exhibited cytotoxicity against several cancer cell lines tested.
