Abstract: AimTo design and synthesize a series of new taxoids with a 5-O-sidechain, and to test the multi-drug resistant reversal activity of these compound on KB/V200 cells which is 180 times more resistant to vincristine. MethodsUsing Sinenxan A as a common synthetic starting material, three different types of 5-O-sidechain molecules were synthesized through different route. For type I compounds, 14-acetoxy of Sinenxan A was selectively removed by hydrolysis, xanthation and reduction with tributyltin; A C-10-oxo group was introduced by PCC oxidation; 5-O-acetyl group was selectively removed by potassium tert-butoxide and finally the side chain was introduced by acylating with the corresponding acid. For type II compounds, 5-O-sidechain was introduced to the 5-deacetyl Sinenxan A which was obtained by selective hydrolysis with tBuOK. For type III compounds, 9-acetoxy group was introduced, then 5-OH was left free by thorough hydrolysis and reacetylation. Acylation at 5-position, the final product was obtained. Structure of the compounds have been confirmed by FABMS and 2DNMR. The activity of the compounds in vitro was tested on KB/V200 resistant cell line using MTT method. ResultsNine compounds showed resistant reversal activity and enhancing the cytotoxicity of vicristine against KB/V200 cells. Compounds I₂, I₃, I₄ restored the sensitivity of KB/V200 towards vicristine to a level of IC₅₀ at 1×10^-8 mol·L^-1 which is better than the positive control Verapamil. ConclusionThe drug resistant reversal activity of taxane derivatives can be affected by substitution at different positions and the length of side chains of Sinenxan A. It is worthy to be further studied.